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452 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Standing/stationary wave |
A wave thaat remains in a constant position with no net energy transfer characterised by its nodes and antinodes |
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Antinode (on a stationary/standing wave) |
The maximum displacement or amplitude on a standing/stationary wave. |
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Node (standing/stationary wave) |
The position of minimum displacement at the equilibrium position on a stationary wave |
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Newtons 1'st law |
An object stays in a state of rest or uniform motion unless acted upon by a resultant force |
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Newtons 2nd law |
The rate of change of momentum is directly proportional to the resultant force and acts in the same direction. F=ma or F=Δ(mv)/Δt |
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Newtons 3rd law |
All interacting objects exert equal and opposite forces (of the same type) on each other. |
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Progressive Wave |
A wave that transfers energy in the direction of motion away from the source |
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Phase difference |
Where two coherent waves have a difference in angle measured in radians |
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Principle of superpositioning |
When two waves meet at a point and interfere constructively or destructively. |
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Constructive Interference |
When two in phase waves meet the resultant wave has a larger amplitude. |
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Destructive Interference |
When two coherent, out of phases waves superpose causing the resultant wave to have a smaller amplitude |
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Path Difference |
Where two coherent waves have a difference in wavelength, measured in metres. |
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Kirchcoff's 1st law |
The total current into a junction must equal the total current out of a junction. ΣI(in)=ΣI(out) |
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Kirchcoff's 2nd Law |
EMF in a loop is equal to the EMF in the battery ΣEMF(loop)=ΣEMF(battery) |
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Assumed resistance of a Voltmeter? |
Infinite |
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Assumed resistance for an Ammeter? |
Negilible |
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EMF |
The electrical energy per unit charge. EMF= E/Q |
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Current |
The flow of charge carriers, eg: electrons. |
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Potential difference |
Work done per unit charge V=W/Q |
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Ohms law |
Current is proportional to resistance with a constant temperature. I∝V |
graph: |
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Internal resistance of a battery |
Resistance of the materials within a battery, or the hindrance in the flow of charge within the battery. |
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What is the definition of current? |
Rate of flow of charge in a circuit, measured in Amperes: I=ΔQ/Δt |
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definition of coulomb |
Amount of charge passing in one second when the current is one ampere: ΔQ=IΔt |
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definition of resistance |
The potential difference in volts divided by the current in amperes: R=V/I in ohms. |
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non-ohmic conductor |
A component that does not have a constant resistance and thus does not follow ohms law |
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What circuit should be used to find the I-V characteristic for a component? |
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I-V characteristic graph for an ohmic conductor |
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I-V characteristic graph for a filament lamp |
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Explain the filament bulb I-V curve (why is it like that?) |
»some electrical energy is transferred to thermal »metal heats up and vibrates (more) »vibrations reduce the flow of charge carriers »current cannot flow easily, resistance increases |
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Why does the IV graph for a filament bulb eventually level off? |
»more current=more thermal energy »increasing resistance »current decreases |
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What is a diode? |
component made from semiconductors designed to restrict current to flow in only one direction. |
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what is the threshold voltage? |
lowest voltage in the forward direction before a diode will conduct »usually 0.6V |
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what is the IV characteristic for a diode? |
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definition of resistivity |
resistance of a 1m length material with a 1m^2 cross-sectional area »measured in Ωm |
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what is the equation for resistivity? |
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what is the impact of length on the resistivity of a wire? |
»longer=more difficult for current to flow »resistance is ∝ to length |
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what is the impact of area on the resistivity of a wire? |
»wider=easier for current to flow |
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what is the relationship between the resistivity of a wire and its ability to conduct electricity? |
» the lower the resistivity the better the conductor |
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what is a semiconductor? |
»have less charge carriers thus not a good conductor »when supplied energy more charge carriers released »resistance decreases |
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what is a thermistor |
a component with a resistance dependant on temperature: »resistance decreases with an increasing temperature |
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what circuit would be used to investigate the resistance of a thermistor? |
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What method would be used to investigate the resistance of a thermistor? |
»use a water bath to control temperature »measure and record temperature for every 5° change »record the corresponding current and potential difference value for this change »calculate resistance and plot graph |
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what is a superconductor? |
material that has zero resistance when cooled below their 'transitional or critical temperature' »no electrical energy is wasted |
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what are the uses of superconductors? |
»power cables »strong electromagnets »electronic circuits etc |
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Practical: determining the resistivity of a wire: basic method |
»calculate cross-sectional area (measure diameter-use A=4πr^2) »set up experiment »attach 'flying lead' and measure length »close switch, measure current and pd »open switch and calculate resistance, repeat to get average »repeat overall process with different lengths »plot graph: average resistance (Ω) against length (m) |
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Practical: determining the resistivity of a wire:experimental set up |
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Practical: determining the resistivity of a wire:graph and calculating resistivity |
gradient: R/L because R/L=ρ/A multiply gradient by A |
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definition of power |
rate of transfer of energy » measured in Watts, W 1W=1Js^-1 |
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What are the equations for power in an electrical circuit? |
P=E/t P=IV P=V^2/R P=I^2R |
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what are the equations to calculate total energy in an electrical circuit? |
E=IVt E=I^2Rt |
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How do you convert electrical energy in kWh to joules? |
multiply by 3.6x10^6 |
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What equation links the electromotive force and internal resistance? |
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expanding brackets gives: ε=IR+Ir substituting V=IR ε=V+v v=lost volts |
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what equation is used to calculate energy lost due to internal resistance? |
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Practical: measuring internal resistance and e.m.f.: circuit used |
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Practical:measuring resistance and emf: what is the basic method? |
»set variable resistor to highest resistance »close switch measure and record current and potential difference. calculate mean »decrease resistance and repeat process for varying resistances »plot V-I graph for mean data and draw lobf |
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Practical:measuring resistance and emf:analysing the graph |
equation V=ε-Ir can be re-arranged to: V=-rI + ε |
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calculating the total emf of cells in a series circuit |
»the charge goes through each cell thus gains energy from each cell |
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Calculating the total emf of cells in parallel. |
The total emf of this arrangement is equal to the emf of one cell »the amount of charge flowing does not increase and only gains emf from the cell it travels through |
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What is a potential divider? |
Circuit with a voltage source and a couple of resistors in series |
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what is the potential divider equation? |
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uses of potential dividers |
»volume control »turn on lights »turn on heating systems |
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When is strangeness conserved during an interaction? |
Only when a proton and neutron are involved |
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what are the masses of a proton and neutron? |
1.67x10^-27 kg |
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what are nucleons? |
the particles that are in the nucleus: protons and neutrons. |
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charge of a neutron |
0 Coulombs |
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charge of an electron or proton |
1.6x10^-19 Coulombs |
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Mass of an electron |
9.11x10^-31 kg or 1/1840 of a nucleon |
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proton number or atomic number |
the number of protons in the nucleus |
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Nucleon number |
The number of protons and neutrons in the nucleus |
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What is the nuclide notation (use letters A,Z and X) |
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what is the specific charge of a particle? |
the ratio of charge to mass of the particle in CKg^-1 specific charge=charge/mass |
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what is an isotope? |
An atom that has the same proton number but a different nucleon number |
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what is the impact of more neutrons in an isotope? |
makes the nucleus unstable which may be radioactive and decay to become stable. |
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what is isotopic data? |
the relative amounts of isotopes in a substance |
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what is a uses of isotopic data? |
carbon dating using the percentage of carbon-14 in an object |
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what are the forces in an atom? |
»electromagnetic repulsion (between protons in nucleus) »gravitational force, (attractive) »strong nuclear force |
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what are the force transmitters for the strong nuclear force? |
Gluons |
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What is the strong nuclear force? |
a fundamental force with a short range which is attractive between 0.5fm to 3fm and repulsive at separations below 0.5fm. responsible for the stability of nuclei. |
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what is the shape of the graph showing the balance of strong force and the electromagnetic repulsive force? |
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what is the most stable element? |
iron, atomic radius of 3fm |
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What is the particle for alpha radiation? |
Helium nucleus |
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What is the alpha radiation's range in air? |
few mm |
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What can stop alpha radiation? |
paper |
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What is the emitted particle for Beta - decay? |
high speed electron |
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What is the emitted particle for Beta + decay? |
high speed positron (anti-electron) |
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What is the range of beta radiation in air? |
few cm |
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What can stop beta radiation? |
aluminium sheet |
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what is the emitted particle for gamma radiation? |
a high energy photon |
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what is gamma radiation's range in air? |
infinite |
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what can stop gamma radiation? |
several cm of lead |
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what is the range of an emitted neutron in air? |
infinite |
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what can stop an emitted neutron? |
concrete |
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what emits alpha radiation? |
»heavy nuclides, proton numbers greater than 82 »small nuclides with too few neutrons |
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what is the general decay equation for alpha radiation and decay? |
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what happens in alpha radiation? |
»nucleon number decreases by 4 »alpha particle emitted from nucleus |
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What energy is released in alpha decay and where does it go? |
Kinetic energy,the majority goes to the alpha particle and little goes to the decayed nucleus »thus velocity of alpha particle is greater than the decayed nuclei's |
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What emits beta - , β¯ radiation? |
» energetic neutron rich nuclei |
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what happens in beta decay? |
»high speed electron emitted by a neutron »anti neutrino ⊽ emitted »neutron turns into a proton »proton number increases by 1 »nucleon number stays the same. »new element formed |
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what is the general equation for beta¯ decay, β¯? |
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What emits beta plus radiation? |
»proton rich nuclei |
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What happens in beta plus decay? |
»high speed positron emitted by a proton »neutrino 𝛎 emitted »proton turns into a neutron »proton number decreases by 1 »nucleon number stays the same. »new element formed |
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what is the general equation for beta plus decay? |
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What is a neutrino, 𝛎? |
A lepton with almost no mass and zero charge. |
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How were neutrino's discovered? |
»missing energy in beta decay discovered due to conservation of energy »another particle must be emitted with the missing energy »due to conservation of charge and mass, must have no charge and almost no mass |
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What is the photoelectric effect? |
The emission of electrons from the surface of a metal when a high frequency photon is absorbed (by the electron). |
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What is stopping potential? |
The maximum negative potential difference that can be applied to a metal surface before an electron escapes from the surface and reaches the other side. |
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What is the work function in the photo-electric effect? |
The minimum energy needed to release an electron from the surface of a metal due to the attractive forces in the metal. |
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What happens to excess energy absorbed by an electron from a photon in the photo-electric effect? |
converted to kinetic energy of the emitted photo-electron |
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What does the stopping potential do? |
»sets a limit to when the current starts to flow »makes the plate the electrons are liberated from positive »attracts the electron back to the original surface |
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What graph can show the relationship between initial kinetic energy and frequency in the photoelectric effect (draw graph) |
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What is the relationship between Kinetic energy and frequency in the photoelectric effect? |
»proportional gradient »area of no proportionality shows work needs to be done to liberate electrons (work function) |
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What is ionisation? |
»the loss or gain of an electron |
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What is an electronvolt |
The kinetic energy gained by an electron when it is accelerated through a potential difference of 1v »1V=1JC^-1 |
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What is the conversion factor between joules and electron-volt? |
1.6x10^-19 »multiply for joules to ev »divide for ev to joules |
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What is excitation? |
When an electron gains energy by absorbing a photon and moves up an energy level |
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What is de-excitation? |
When an electron emits a photon losing energy and moves down an energy level or levels. |
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What is the energy needed to move up an energy level called? |
»discrete energy |
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What is the impact of a magnetic field on an Alpha particle? Why? |
»subtly repelled causing a slightly curved path »large mass, low velocity thus harder to repel. |
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What is the impact of a magnetic field on a Beta particle?Why? |
»repelled significantly, path is curved »small mass, high velocity thus easier to impact. |
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What is the impact of a magnetic field on Gamma radiation?Why? |
No change, has no charge and no mass. |
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Pair Production |
A photon creates a particle and it's corresponding anti-particle »only when the photon has enough energy to produce the total rest mass of the two particles
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What is the equation to calculate the minimum photon frequency required for pair production? |
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Annihilation |
when a particle collides with its corresponding antiparticle. All mass is converted to energy as a high energy photon. |
Equation: |
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when do anti-particles come to be? |
»high-energy collision experiments »interactions with cosmic rays and radioactive decay |
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What are Positron Emission Tomography scanners? |
scan producing 3D images of the body using emitted positrons from an ingested positron emitting isotope. |
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How do positron emission tomography, PET scanners work? |
»positrons produced by beta plus decay » positron collides with an electron producing photons (annihilation) »photons detected |
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What are the dangers of PET scanners? |
»frequent use will damage the brain. |
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What is a virtual particle? |
a particle that exists for a short amount of time eg: an exchange particle. |
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What are the four fundamental forces? |
»strong nuclear force »Electromagnetic force »weak nuclear force »gravity |
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What does the electromagnetic force do in the nucleus? |
repels protons away from each other |
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What does the electromagnetic force do in the atom? |
attracts the oppositely charged nucleus to the negatively charged electrons |
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What happens to the electromagnetic force with an increasing distance? |
decreases |
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What is the weak force? |
A fundamental force that has a short range and can change the identity of a particle by the exchange of bosons. |
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What are W bosons? |
The particle mediator of the weak force. They have no mass, positive or negative charge and a short range. |
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What is a hadron? |
a particle made up of quarks that is affected by the strong nuclear force. |
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What is a baryon? |
A type of hadron composing of three quarks. eg: protons and neutrons |
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What is a meson? |
type of hadron composing of a quark and anti quark. dont have baryon numbers.p[d eg: pions and kaons |
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What is a lepton? |
A fundamental particle that is ONLY affected by the weak nuclear force. eg: electrons, muons and neutrinos. |
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What is a Fundamental particle? |
A particle that cannot be broken down into anything else |
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What is a Feynman diagram? |
a visual representation of particle interactions showing the exchange forces, time is upward. |
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What is the Feynman diagram for a neutron-neutrino interaction? |
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What is the Feynman diagram for a proton- anti neutrino interaction? |
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What is the Feynman diagram for beta- decay? |
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What is the Feynman diagram for beta+ decay? |
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What is the Feynman diagram for electron capture? |
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What do exchange particles transfer? |
»momentum »energy »charge (W- and W+ bosons) |
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what is the Feynman diagram for the electromagnetic repulsion of two electrons? |
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what is the Feynman diagram for the electromagnetic repulsion of two positrons? |
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What are the baryon numbers for neutrons and protons, matter and anti-matter? |
»1 for protons/neutrons »+1 for matter »-1 for anti-matter |
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what are the key facts about keons? (strangeness and composition) |
»have strangeness »made from quarks and anti quarks |
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what are the key facts about pions?(strangeness and composition) |
»no strangeness »made from quarks and anti-quarks |
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what two properties do quarks have (excluding mass)? |
»charge »strangeness |
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What is the equation to calculate rest energy? |
Rest energy is equal to: total energy before -- kinetic |
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what fundamental forces do leptons interact through? |
» weak interaction »electromagnetic interaction (if charged) »gravitational interaction. |
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What must be conserved when leptons interact? |
lepton number |
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what fundamental forces do hadrons interact through? |
»all four fundamental forces: weak nuclear strong nuclear gravitational electromagnetic |
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What must be conserved when baryons interact? |
»strangeness »baryon number »charge |
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What is the quark combination of a Pion, π°? |
Up quark and anti up |
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what is the quark combination of a proton? |
uud or up up down |
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What is the quark combination for a k° |
down and anti-strange |
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what is the quark combination of a neutron? |
udd or up down down |
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what is the quark combination for a pion +, π+? |
up anti-down |
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what is the quark combination for a π¯, pion ¯? |
down anti-up |
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What do K mesons decay into? |
»π mesons »muons or anti-muons »anti-neutrinos or neutrinos |
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What do charged pi mesons decay into? |
»muons and anti-neutrinos or »anti muons and neutrinos |
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what do charge-less pions decay into? |
high energy photons |
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What is the strangeness of a K°and K+ meson? |
+1 |
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hat is the strangeness of a K- and K+ meson? |
-1 |
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What are cosmic rays? |
Radiation in the form of charged particles that come from space and hit earth. |
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Where are cosmic rays produced? |
naturally: super novas artificially: hadron collider, CERN |
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What is quantisation? |
When electrons only absorb photons of discrete energy |
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What is the ground state? |
The lowest energy level of an atom. |
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How do fluorescent tubes work? |
»thermionic emissions »electrons turn into photons »mercury atoms absorbs photon and is excited »mercury atom de-excites emitting a UV or visable light photon »phosphorous atom absorbs UV photon, excites, de-excites emitting visable light photon. |
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What is the process of excitation? |
» electron absorbs a photon »electron moves up an energy level, is excited »electron de-excites »can de-excite to multiple levels producing different frequencies of photons »electron de-excites to ground state. |
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What are cosmic ray showers? |
lots of high-energy particles eg: kaons and pions, produced from cosmic rays interacting with molecules in the atmosphere |
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How can tracks of high-energy particles and radiation be observed? |
cloud chamber |
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What is a diffraction grating? |
A slide or thin object that contains lots of equally spaced slits very close together. Used to show the diffraction patterns of waves. |
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What is a line spectrum? |
A pattern of lines produced by photon being emitted or absorbed by electrons moving between energy levels in an atom. |
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What is line absorption spectrum? |
A line spectrum with black lines corresponding to different wavelengths of light that have been absorbed. |
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Line emission spectrum |
A spectrum of bright lines on a dark background corresponding to different wavelengths of light that have been emitted. |
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what is diffraction? |
When waves spread out as they pass through a narrow gap or go around obstacles. |
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what is wave particle duality? |
all particles have both particle and wave properties. Waves can also show particle properties |
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What is the de-broglie wave-length equation? |
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What is electron diffraction? |
Where an electron gun fires electrons at a graphite crystal. »the electrons pass through and diffract »the diffraction pattern produced is similar to the diffraction pattern of waves. |
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What is reflection? |
When a wave 'bounces back' when it hits a boundary. |
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What is refraction? |
When a wave changes direction as it enters a different medium as a result of the wave slowing down or speeding up. |
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What is displacement, x? |
The distance the object has travelled from the original or undisturbed position measured in metres. |
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What is Amplitude,A? |
The maximum displacement of a wave from the equilibrium position. measured in metres. |
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What is wavelength? |
The length of one whole oscillation, where the oscillating object has moved back to it's original position. measured in metres. |
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What is the time period, T? |
The time taken for one complete oscillation. measured in seconds. |
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What is frequency, f? |
The number of oscillations per second,measured in Hz or s^-1. |
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What is phase? |
a measurement of the position of a certain point of a wave along the wave cycle in radians. |
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What is the relationship between frequency and time period? |
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What is the equation to calculate wave speed? |
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What is the speed of an electromagnetic wave in a vacuum, c? |
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How can you measure the speed of sound? |
»use two microphones a set distance apart with separate inputs (signals can be recorded separately) »use a signal generator to produce a sound from a loudspeaker. »use a computer to record the time between the first and second microphone (the first peak) »use d=Sxt to calculate speed. |
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How can you measure the wave speed in water using a ripple tank? |
»record water depth »use a dipper to create vibrations in water »use strobe light (light that flashes periodically) to make vibrations visible »increase frequency of strobe light from 0 until the waves don't appear to move »frequency of strobe light= frequency of wave »record the distance between the adjacent peaks »use c=λf for speed. |
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What is a transverse wave? |
a wave where the oscillations are perpendicular to the propagation of energy eg: electromagnetic waves |
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What is a longitudinal wave? |
a wave where the oscillations are parallel to the propagation of energy eg: sound waves |
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What is polarised wave? |
A wave with all oscillations restricted to one plane or direction |
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what is a polarising filter? |
a filter that restricts the oscillations of a wave to one plane. |
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what waves can be polarised? |
ONLY transverse waves. |
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what are the applications of polarised light or polarisation? |
»sunglasses »glare reduction »improvement of tv and radio signals |
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What is in-phase? |
when two waves have a phase difference of 0 or 360° or 0 and 2π radians |
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What is out of phase? |
When two waves have a phase difference of 180° or π |
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How can you demonstrate a standing wave? |
»setting up a driving oscillator at the end of a stretched string and the other end fixed. |
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what are resonant frequencies? |
a frequency at which a stationary or standing wave is formed because an exact number of waves are produced in the time it takes for a wave to get to the other end of the vibrating medium and back again. |
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What is happening at the node of a stationary/standing wave? |
complete destructive interference |
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What is happening at the anti-node of a stationary/standing wave? |
constructive interference |
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What is the first harmonic? |
the lowest frequency at which a stationary/standing wave are formed where the wavelength is double the length of the vibrating medium. λ=2L |
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What is the second harmonic? |
a resonant frequency where the wavelength is equal to the length of the vibrating medium. Twice the frequency of the first harmonic. λ=L |
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What is the third harmonic? |
A resonant frequency at which one and a half wavelengths fit along the vibrating medium. the frequency is three times the first harmonic. λ=1½L |
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what are the other demonstrations of stationary or standing waves? Briefly how do they work? |
»STATIONARY MICROWAVES reflecting microwave beam at a metal plate, waves superpose. meter/loudspeaker receives no signal at nodes and anti nodes. »STATIONARY SOUND WAVES powder in a tube of air , powder is undisturbed at nodes. |
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What is the equation to calculate resonant frequency? |
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What is the equation to calculate mass per unit length,μ? |
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What is the equation to calculate the tension of a string? |
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Investigating resonant frequency:equipment needed |
»signal generator »vibration transducer »string of length l »pulley »masses »work surface »G clamp |
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Investigating the resonant frequency:basic method (4 steps) |
»calculate the mass per unit length, μ »calculate tension in the string »turn on signal generator and vary frequency and find the first harmonic »keep all factors constant and vary one: »vary length »vary mass and thus tension T »vary string for different mass per unit lengths. |
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What are the factors affecting resonant frequency? |
»LENGTH »MASS PER UNIT LENGTH, μ »TENSION |
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how does a longer string affect the resonant frequency? |
longer string=lower r.f. as the λ is larger and c is constant, f will be smaller: c=fλ |
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How does a larger mass per unit length, μ affect resonant frequency? |
larger μ= lower r.f. as the wave will travel down the the string at a slower speed thus f decreases. |
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How does a lower tension on the string affect the resonant frequency? |
waves will travel down the string at a slower speed when there is little tension. |
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when is diffraction unnoticeable? think gap size. |
When the gap is much bigger than the wavelength of the wave. |
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When is diffraction noticeable?think gap size. |
When the gap is several wavelengths wide. |
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When is there the most diffraction? |
when the gap is the same-size as the wave-length. |
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what happens to a wave when the gap is smaller than the wavelength? |
The wave is mostly reflected back. |
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What is the affect of a wider object/obstacle in diffraction around obstacles? |
A longer shadow (where the wave is blocked) as there is less diffraction around the object. |
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What is mono-chromatic light? |
a light of a single wave-length |
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What is a laser light? |
a coherent and monochromatic light. |
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What is the diffraction pattern of a monochromatic light? |
»bright central fringe and alternating dark and bright fringes of decreasing intensity. »bright fringes due to constructive interference »dark fringes due to destructive interference. |
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What is the diffraction pattern of white light? |
»bright central fringe and alternating dark and bright fringes with decreasing intensity. in bright fringes there are light spectrums of decreasing clarity. |
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What is intensity? |
Power per unit area. for monochromatic light all photons have the same energy thus an increase in intensity is an increase in the number of photons. |
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what is the impact of increasing the slit width on the central maximum? |
decreases the amount of diffraction, the central maximum is narrower and the intensity is higher. |
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What is the impact of increasing the wavelength on the central maximum? |
increases the amount of diffraction. The central maximum is wider and the intensity is lower. |
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What is two-source interference? |
When waves from two sources interfere to produce a pattern |
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Define coherent. |
when two sources or waves that have the same wavelength and frequency and are in-phase or have a fixed phase difference between them. |
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What is a maxima? |
A point in an interference pattern where the intensity is locally brightest, and caused by constructive interference |
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What is a minima? |
A point in an interference pattern where the intensity is locally lowest, caused by destructive interference. |
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When does constructive interference occur in an interference pattern? |
when path difference=nλ |
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When does destructive interference occur in an interference pattern? |
when path difference=(n+½)λ |
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What are the safety precautions needed when dealing with lasers? (5 safety cautions) |
»never shine a laser towards someone »wear laser safety goggles »avoid shining it t a reflective surface »have a warning sign on display »turn the laser off when not in use |
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What is the double slit formula? |
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What is the 'zero order line'? |
the line of maximum brightness at the centre of a diffraction grating interference pattern. it's in the same direction as the incident beam. |
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Where is the first order line? |
next to the zero order line, on either side. |
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What is the diffraction grating equation? |
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What is the impact of increasing wavelength λ, on the interference pattern? shown by the equation dsinθ=nλ |
Increasing λ increases θ, the larger the wavelength,the more the pattern will spread out. |
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What is the impact of increasing the distance between the slits, d, on the interference pattern? shown by the equation dsinθ=nλ |
increasing d decreases θ, the larger the distance between the slits the less the pattern will spread out. |
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What are the applications of diffraction gratings? |
»spectra of light »light absorption spectra »x-ray crystallography |
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what is optical density? |
The property of a medium that describes how fast light travels through it. light moves slower through a medium with a higher optical density.measured by the material's refractive index. |
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What is the absolute refractive index, n, of a material? |
The ratio between the speed of light in a vacuum c and the speed of light in a material Cs. |
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What is the equation for the refractive index? |
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What is the relative refractive index? |
The ratio of the speed of light in one material to the speed of light in a second material. |
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What are the equations to calculate the relative refractive index? |
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What is Snell's law of refraction? |
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Which way does the light bend when travelling from a less optically dense material to a more optically dense one? |
Towards the normal |
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Which way does the light bend when it travels from a more optically dens material to a less optically dense one? |
Away from the normal |
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What is the critical angle? |
The angle of incidence at which the angle of refraction is 90° |
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What is the angle of incidence? |
The angle that incoming light makes with the normal boundary. |
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What is the angle of refraction? |
The angle that refracted light makes with the normal boundary. |
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What is the equation to calculate the critical angle? |
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What is total internal reflection? |
when all light is completely reflected back into the medium at a boundary with another medium, instead of being refracted. only when the angles of incidence are greater than the critical angle. |
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What are the two conditions for total internal reflection? |
»angle of incidence is greater than the critical angle »incidence substance has a larger refractive index than the secondary substance |
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What is an optical fibre? |
thin flexible tube of glass or plastic that can carry light signals using total internal reflection. |
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What are the applications of total internal reflection? |
»transmit phone and TV signals »transfer of information |
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What are some of the advantages of fibre optics compared to copper cables? |
»signal can carry more information »no electrical interference »cheaper to produce »minimal signal loss |
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What are the the three types of signal degradation? |
»Absorption »Modal dispersion »material dispersion |
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What is absorption? |
Where some of the signal's energy is absorbed by the material. Energy loss causes a reduction in the signal's amplitude. |
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What is modal dispersion? |
When a beam of light passes through a fibre optic and the signal strength deteriorates. |
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What is material dispersion? |
Dispersion caused by different wavelengths of light travelling at different speeds through the material of an optical fibre. |
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What is pulse broadening? |
When signal in an optical fibre gets wider/broader as it is transmitted due to dispersion. |
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What can be done to reduce the signal degradation in an optical fibre? |
use optical fibre repeaters to regenerate the signal. |
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What is a scalar quantity? |
quantity that has magnitude but no direction. eg: mass, time, distance, energy |
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What is a vector quantity? |
a quantity that has both magnitude and direction. |
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How can you find the resultant value of two vectors? |
»use a scale diagram »use trigonometry |
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What is the equation to find the horizontal component of a vector? |
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What is the equation to find the vertical component of a vector? |
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What is a free-body force diagram? |
Diagram showing all of the forces acting on a body, but not the forces it exerts. Arrow labels shows the size and direction of the force. |
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define equilibrium? |
When all forces acting on a body cancel each other out. |
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what is the acceleration of a body in equilibrium? Why? |
zero, all forces cancel each other out. |
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What is the motion of a body in equilibrium? |
either stationary or constant velocity. |
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What is a vector triangle or vector polygon? |
Where all forces acting on an object in equilibrium form a closed loop. |
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What are the two methods to solving equilibrium problems? |
use a vector triangle or resolve the forces in two perpendicular directions |
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How do you resolve forces in two perpendicular directions? |
use trigonometry |
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What is a moment? |
the turning effect of a force around a turning point. |
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What is an object's mass? |
the amount of matter in the object. unit: Kg |
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What is an object's weight? |
The force experienced by a mass due to a gravitational field. W=mg |
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What is the gravitational field strength on earth? |
9.81 Nkg^-1 |
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What is the equation for moments? |
M=fd m=moment f=force d=perpendicular distance. |
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What is the principle of moments? |
The sum of the clockwise moments is equal to the sum of anti-clockwise moments for a system in equilibrium. |
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what is a lever? |
a structure made of a rigid object rotating around a pivot, in which an effort force works against a load force. |
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What is a couple? |
a pair of forces of equal size which act parallel to each other in opposite directions. |
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What is the centre of mass of an object? |
The point at which the objects weight acts through. |
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How can you find an objects centre of mass? |
hang an object freely from one corner »draw a vertical line down alongside the plumb line »hang the object from different points and repeat »centre of mass is the point where all lines cross. |
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In what position with the centre of gravity will an object fall over? |
when the centre of gravity's line of action falls out of the object's base area. |
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What is the impact of increasing the centre of mass and decreasing the base area of an object? What about the reverse? |
Makes the object LESS stable , opposite makes the object MORE stable |
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What happens to the force experienced by a support of an object if it is moved closer to the centre of mass? |
the fore experienced is greater in magnitude. |
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What is the speed of an object? |
Rate of change of distance of an object, scalar quantity. |
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What is an objects displacement? |
The rate of change of an objects displacement, vector quantity. |
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What is an objects acceleration? |
The rate of change of an object's acceleration. |
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What is the suvat equation for no s? |
v=u+at |
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What is the suvat equation for no u? |
2 s=vt-½at |
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What is the suvat equation for no v? |
2 s=ut+ ½at |
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What is the suvat equation for no a? |
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What is the suvat equation for no t? |
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What is a displacement time graph? |
Graph with displacement on y axis, time on x axis and velocity as the gradient. |
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How do you calculate the velocity of an object using a displacement time graph? |
calculate the gradient of the graph. |
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What is acceleration on a displacement time graph? |
rate of change of the gradient |
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What is the gradient for an accelerating object on a distance-time graph? Which way for acceleration and deceleration? |
a curved gradient, increasing for acceleration, decreasing for deceleration. |
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What is an objects instantaneous velocity? |
velocity at a particular moment in time. |
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What is objects's average velocity? |
The total change in displacement of the object over the total time taken. |
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What is a velocity time graph? |
a graph with velocity on y-axis, time on x-axis and acceleration for the gradient. |
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How can you calculate the acceleration on a velocity time graph? |
Calculate the gradient |
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on a graph how is uniform acceleration shown? |
straight line |
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What does a steeper gradient show on a velocity time graph? |
greater acceleration. |
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What is the difference between a velocity time graph and a speed time graph? |
Velocity time graph can have negative values |
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how can you find the total distance travelled by an object? |
d= average speed x time |
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What does the area under the velocity time graph represent? |
Displacement |
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what does the area under a speed time graph represent? |
distance |
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How is non-uniform acceleration shown on a velocity time graph? |
A curved line increasing gradient is acceleration.decreasing is deceleration |
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What are the advantages of using data-loggers? |
»data more accurate »larger sampling rate »data displayed real time. |
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What is an acceleration time graph? |
acceleration on the y axis and time on the x axis, positive gradients show acceleration and negative gradients show deceleration. |
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how can you find the velocity on an acceleration time graph? |
Δv=a x t area under the graph |
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Which direction is the acceleration of an object? |
the direction of the net or resultant force. |
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What is free fall? |
the motion of an object undergoing an acceleration of g (9.81 ms^-2) |
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What was Galileo's free-fall investigation? |
Rolled a ball down a slope, at different fractions of the total length. discovered the ball accelerated at the same rate. |
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what is acceleration independent of? |
mass of the object |
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what is the sign convention for the direction of objects in free-fall, and time? |
upwards is positive downwards is negative time is always positive. |
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What are the equations of motion for free-fall, with no initial velocity? |
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When there is an initial velocity upwards or downwards what is the impact on the equations of motion? |
equations are normal, acceleration is g |
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What is projectile motion? |
motion with a constant horizontal velocity and a vertical velocity affected by acceleration due to gravity. |
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What is the method you would use when calculating projectile motion at an angle? |
»resolve the initial velocity into its components »use vertical component to calculate maximum height and duration of flight »use horizontal component to calculate the maximum distance. |
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What is the impact of the resistive force of drag on projectile motion? |
reduces the horizontal and vertical velocity thus reducing the horizontal distance travelled and the maximum height Angle of descent steepened. |
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what is friction? |
A force that opposes motion It acts in the opposite direction to motion. Arises when two objects are moving past each other, or when an object moves in a fluid. |
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What is friction in a fluid called? |
drag eg: air resistance |
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What is a fluid? |
Either liquid or gas. |
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What are the three factors which affect fluid friction/drag? |
»viscosity of fluid » the objects speed (proportional) »shape of the moving object larger the area=greater resistive force. |
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What energy do frictional forces convert kinetic energy to? |
Thermal energy. |
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What is lift? |
An upwards force acting on an object moving through a fluid. |
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What is terminal speed/velocity? |
The speed at which the driving forces equal the frictional forces. |
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What are the two main methods of increasing an objects maximum velocity? |
»increase the driving force »reduce the frictional force |
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What is the velocity time graph for terminal velocity? |
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What is the acceleration time graph for terminal velocity? |
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What are the three main stages to reaching terminal velocity? |
»constant driving force »as speed increases drag force increases, resultant force reduced. »driving force and drag force are equal, there is no net force. |
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what is the velocity time graph for a parachutist? |
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What is momentum? |
The product of an objects mass and velocity. p=m x v |
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What is the principle of linear momentum? |
The total linear momentum before a collision is equal to the total linear momentum after the collision. assuming no external forces act. |
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What is an elastic collision? |
Where the momentum is conserved and kinetic energy is conserved. NO energy is dissipated. |
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What is an in-elastic collision? |
Where some of the kinetic energy is dissipated. Linear momentum is always conserved. |
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What is the equation showing the change in momentum? |
Δ(mv)= mv - mu |
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What is impulse? |
the product of force and time FΔt=Δ(mv) the area under a force time graph. |
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What is the affect of increasing the time taken for a force to impact? |
Force of the impact is reduced. |
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What features of car safety reduce the impact force during a collision? |
»Crumple zones »seat belts »air bags |
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What is work done? |
The amount of energy transferred from one form to another when a force moves an object through a distance. |
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How do you calculate the work done? |
W= Fs w: Work done, J F:force causing motion, N s:distance moved, m |
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what is the equation for work done at an angle? |
W=Fs cos(θ) |
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What is the equation for power? |
P=ΔW/Δt |
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What is the definition of the unit Watt? |
rate of energy transfer equal to 1 joule per second. |
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How do you calculate the work done for a variable force? |
»plot a force-distance graph »calculate the area under the graph. |
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What is the equation that links power and velocity? |
P=Fv |
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What is the equation that links power and velocity with the motion acting in a different direction? |
P=Fvcos(θ) |
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What is the principle of the conservation of energy? |
Energy cannot be created or destroyed. Energy can be transferred from one form to another but the total amount of energy in a closed system will not change. |
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What is efficiency? |
The ratio of useful energy given out by a machine to the amount of energy put in the machine. |
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What is the equation for efficiency in terms of energy? |
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What is the equation for efficiency in terms of power? |
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What is the equation for kinetic energy? |
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What is the equation for gravitational potential energy? |
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What is density? |
The mass per unit volume of a material or object. kgm^-3 ρ=m/v |
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What is Hooke's law? |
The extending or compressing force is directly proportional to the extension up to the limit of proportionality. F∝ΔL |
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what is the equation for Hooke's law? |
F=kΔL k is the stiffness constant/spring constant. |
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What does a tensile force do to a spring? |
stretches/extends a spring |
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What does a compressive force do to a spring? |
compresses the spring |
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What is the limit of proportionality? |
Where the forces applied are proportional to the extension of a material aka: Hooke's law limit. |
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What is the elastic limit of a material? |
The forces or stress beyond which a material will be permanently stretched. |
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What is elastic deformation? |
When the material returns to it's original shape once the forces acting are removed. |
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What happens to the atoms during an elastic deformation? |
moved small distances relative to their equilibrium position without changing position in the material.When the load is removed the atoms return to the equilibrium positions. |
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What is plastic deformation? |
when the material is permanently stretched once the loading forces are removed. |
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What happens to the atoms in a material during plastic deformation? |
The atoms moved from their equilibrium position but once the load is removed they don't return. |
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What is tensile stress? |
The force applied ,F, divided by the cross-sectional area,A. stress=F/A. in Nm^-2 or Pascals |
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What is tensile strain? |
The change in length (extension or compression) over the original length. strain=ΔL/L NO UNITS |
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What is the ultimate tensile stress or UTS? |
The maximum stress a material can withstand |
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What is the breaking stress, B? |
The lowest stress that is big enough to break a material. |
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What is the elastic strain energy? |
The work done in stretching a material stored as potential energy. |
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What is the equation for elastic potential energy? |
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What is the transfer from energy as a vertical spring with a mass is stretched? |
Elastic potential energy is transferred to kinetic energy as the spring contracts and gravitational potential energy as the mass gains height. |
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What is the 'overall' transfers of energy in an oscillating spring? |
change in kinetic energy=change in potential (gravitational and elastic) |
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What is the young's modulus of a material? |
The tensile stress over tensile strain of a material up to its limit of proportionality. E=stress/strain |
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How do you find the young's modulus of a material for a stress strain graph? |
Find the gradient as stress/strain= young's modulus. |
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What does the area under a stress strain graph represent? |
The strain energy per unit volume. |
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How can you calculate the energy per unit volume? |
energy per unit volume: ½ x stress x strain |
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What is the yield point of a material? |
The stress at which a large amount of plastic deformation takes place with a constant or reduced load |
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What is a force extension graph? |
A graph showing the force-extension behaviour specific to a material and it's dimensions. |
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What is the typical force-extension graph for a metal wire? |
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What is represented by the area of the graph between the loading and unloading lines of a force extension graph? |
the work done to deform the wire. |
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Why are the loading and unloading lines for a force-extension graph of a metal wire parallel? |
As the stiffness constant k is the same and the force on the atoms of the material are the same. |
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What is a brittle material? |
a material that does not deform plastically, but breaks when the stress acting reaches a certain point. |
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What is the stress strain graph for a brittle material? |
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What is the force-extension graph for a brittle material? |
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What are examples of brittle materials? |
»glass »ceramics »rocks |
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what is brittle fracture? |
When a stress applied to a material causes tiny cracks at the materials surface to get bigger until the material breaks completely. |
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What is a radian? |
The unit of measurement for angles.There are 2π radians in a complete circle. |
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What is the angle in radians equal to in a circle?? |
The arc-length divided by the radius |
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How do you convert from degrees to radians?? |
multiply the angle by π/180 |
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What is angular speed/velocity/frequency? |
The angle an object rotates through per second. measured in rads^-1 |
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What is the equation to calculate angular speed from the angle? |
ω=θ/t ω:angular speed, rads^-1 θ:angle, radians t=time,seconds |
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What is the equation linking angular speed with linear speed? |
ω=v/r ω:angular speed v:linear speed r:radius of the circle of rotation |
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What is the equation to calculate angular speed from frequency? |
ω=2πf |
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What is the equation that links frequency and time period? |
f=1/T |
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What is the centripetal acceleration? |
The rate of change of angular velocity |
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What is the centripetal acceleration directed towards? |
centre of the circle. |
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what is the equation for the centripetal acceleration using linear velocity? |
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What is the equation for the centripetal acceleration using angular velocity, ω? |
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What is the centripetal force? |
The force acting on an object during circular motion, directing towards the centre of the circle and is responsible for the circular path. |
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What is the equation for centripetal force using linear velocity? |
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What is the equation for centripetal force using angular velocity? |
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What is The definition of simple harmonic motion? |
The acceleration is directly proportional to the displacement but acts in the opposite direction a∝-x |
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What is the equation for simple harmonic motion? |
a=-ω^2 - x |
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What is the graph for displacement time for simple harmonic motion? |
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How do you calculate the velocity from the displacement time graph for simple harmonic motion, what impact does this have on the graph? |
find gradient graph is shifted to the left by π/2 |
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What is the graph of velocity for shm? |
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When on the graph of velocity-time for SHM is acceleration maximum? |
When the gradient is at its maximum point, the equilibrium position. |
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What is the graph of acceleration -time for SHM? |
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What are the energy transfers for a pendulum during simple harmonic motion? |
Gravitational potential energy and kinetic energy |
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What are the energy transfers for a vertical mass-spring system in simple harmonic motion? |
Elastic potential energy and kinetic energy |
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When is kinetic energy maximum during simple harmonic motion? |
at the equilibrium position |
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When is the potential energy maximum during simple harmonic motion? |
At the maximum displacements or Amplitudes |
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What is the graphical representation of energy transfers in simple harmonic motion? |
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What is the mechanical energy? |
The sum of potential and kinetic energy of an object. |
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What is the equation to calculate the displacement,x for any object undergoing SHM? |
x=A cos (ωt) x:displacement,m A:amplitude,m ω:angular frequency rads^-1 t:time,s |
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What is the equation to calculate the acceleration of an object in SHM? |
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What is the equation to calculate maximum acceleration of an object during SHM? |
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what is the equation to calculate the velocity of an object in SHM? |
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What is the equation to calculate the maximum velocity of an object in SHM? |
Vmax= ωA v:velocity ms^-1 ω: angular frequency, rads^-1 A: Amplitude, m |
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What is a simple harmonic oscillator, SHO? |
A mass spring oscillating system |
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What is the restoring force for a simple harmonic oscillator? |
The force that pushes or pulls the mass back to the equilibrium position. |
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What is the equation to calculate the restoring force? (same as Hooke's law) |
F=kΔL F:restoring force,N k: spring constant,Nm^-1 ΔL:displacement,m |
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What is the equation for a the time period of a mass oscillating on a spring? |
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What is the equation for the time period of a pendulum in SHM? |
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What is a free vibration? |
The oscillation of an object with no transfer of energy to or from the surroundings |
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What frequency does a free vibration oscillate at? |
the object's natural frequency or resonant frequency |
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What is a forced vibration? |
The oscillation of an object due to an external driving force. |
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What is the frequency of a forced oscillation? |
The driving frequency |
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What happens when the driving frequency is 'much less' than the oscillators natural frequency? |
The two oscillators will be in phase |
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What happens when the driving frequency is much greater than the natural frequency |
The oscillator wont be able to keep up thus the two will be in antiphase |
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What is resonance? |
When the driving frequency is equal to the natural frequency and thus oscillates with a rapidly increasing amplitude. |
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What will happen with prolonged resonance? |
The system will break. |
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What is damping? |
A force which causes an oscillating object to loose energy and so causes the amplitude of the object to decrease. |
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What are the three types of damping? |
light and heavy damping critical damping over damping |
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What is light damping? |
Damping that takes a long time to stop oscillating, amplitude reduces by small amounts each period. |
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What is critical damping? |
reduces the amplitude in the shortest possible time |
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What is over damping? |
systems that are overdamped, take longer to reach equilibrium than critical damping. |
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What is the impact of damping on resonance peaks? |
The heavier the damping the smaller the increase in amplitude during resonance. |
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What is an example of damping? |
Tuned mass dampers, eg: Taipei 101 |
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