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90 Cards in this Set
- Front
- Back
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What are known are nucleons? |
Protons and Neutrons |
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What does the electron number tell about the chemical properties of the element? |
The element’s reactions and chemical behaviour depend on the number of electrons. |
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What is the nuclide notation? |
The nucleon number (mass number) - A, the proton number (atomic number), X - element symbol |
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What is the equation for Specific Charge? |
The ratio of a particle’s charge to its mass. Specific charge = charge/mass |
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Define an isotope. |
Atom with the same number of protons but different number of neutrons. |
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What is known as isotopic data? |
The relative amounts of different isotopes on an element present in a substance. |
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What does the electromagnetic force do in the nucleus? |
Causes the positively charged protons in the nucleus to repel each other. |
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What does the gravitational force do in the nucleus? |
Causes all the nucleons in the nucleus to attract each other due to their mass. |
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What is the name of the attractive force which holds the nucleus together? |
The strong nuclear force. |
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How much is one fm in m? |
1 x 10^-15 |
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Draw and label diagram of strong nuclear force + explain. |
The strong nuclear force is repulsive for very small separations of nucleons (less than about 0.5 fm). As nucleon separation increases past about 0.5 fm, the strong nuclear force becomes attractive. It reaches maximum attractive value, and falls rapidly towards zero after about 3 fm. The electromagnetic repulsive force extends over a much larger range (infinitely, actually) |
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What is known as nuclear decay? |
Unstable nuclei will emit particles to become more stable, this is known as nuclear decay. |
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Describe alpha decay. Write equation. |
Alpha decay only happens in very big atoms, like uranium and radium. The nuclei of the atoms are too big for strong force to keep them stable. So to make themselves more stable, they emit an alpha particle, from their nucleus. |
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Describe beta minus decay. + equation |
Beta minus decay is the emission of an electron from the nucleus along with an antineutrino particle. It happens in isotopes that are neutron rich. When nucleus ejects a beta particle, one of neutrons in nucleus is changed into a proton. The antineutrino carries away some energy and momentum. neutron -> proton + electron + antielectron neutrino |
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Why was the existence of the neutrino hypothesised? |
Law of conservation of energy. |
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What is the electromagnetic spectrum? + diagram and label |
Continuous spectrum of all the possible frequencies of electromagnetic radiation. |
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Complete the sentence: ‘’ the higher the … of electromagnetic radiation, the greater its … ‘’ |
Frequency, energy |
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Define photons. |
EM waves (and energy they carry) can only exist in discrete packets. These wave packets are called photons. |
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What is the equation for photons? |
E=hf, E= energy of one photon, h= Planck’s constant, 6.63 x 10^-34 Js, f=frequency of light in Hz. |
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What is the equation for frequency, wavelength and speed of light? |
f=c/𝝀 (f= frequency in Hz, C=speed of light in a vacuum = 3.00 x 10^8 ms^-1, 𝝀=wavelength in m) |
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What are the two groups of particles broken down into? |
Matter and antimatter. |
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Are the masses, and rest energies the same of the particles and antiparticles? |
Yes. |
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Define pair production. |
When energy is converted into mass you get equal amounts of matter and antimatter. |
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In what instances does pair production occur? |
When there is enough energy to produce masses of the particles. |
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What does pair production produce and why? |
It must always produce a particle and its corresponding antiparticle, due to certain quantities having to be conserved. |
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What is the minimum energy needed for pair production? |
The total rest energy. The rest energy of a particle is the amount of energy that would be produced if all of its mass was transformed into energy. |
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What is the equation for pair production? |
E min = 2E0 |
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How do you convert MeV to J? |
1MeV x 106= eV1eV x 1.60 x 1019=J |
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Describe annihilation. |
When a particle meets its antiparticle the result is annihilation. All the mass of the particle and antiparticle gets converted back to energy in the form of two gamma ray photons. Antiparticle can usually only exits for a fraction of a second before this happens, so you don’t get them in ordinary matter. |
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How do PET scans work? |
PET scanners in hospitals work by putting a positron-emitting isotope into the bloodstream, and detecting the gamma rays produced by the electron-positron annihilation that occurs. The gamma rays are always produced in pairs moving in the opposite directions, so they’re easy to distinguish from other gamma rays. The gamma rays are detected by rings. |
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What are the particles that can feel the strong nuclear force called? |
Hadrons. |
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What are hadrons made out of? |
Quarks. |
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What are the two types of hadrons? |
Baryons and mesons. |
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What are baryons? |
Protons and neutrons. |
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What do unstable baryons decay into? |
Protons. |
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What interaction is between mesons and baryons? |
The strong force. |
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What are pions? |
The lightest mesons, there are +, - and 0 pions. They are the exchange particle of the strong nuclear force. |
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What are kaons? |
Kaons are heavier and more unstable than pions, they have a short lifetime and eventually decay into pions. |
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Define leptons. |
Leptons are fundamental particles and they do not feel the strong nuclear force. Only interact with other particles via the weak interaction. |
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Are electrons stable or unstable leptons? |
Stable. |
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Define muon. |
A heavy electron, unstable, which eventually decays into ordinary electrons. |
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What type of interactions can neutrinos take place in? |
Weak interactions. |
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What is the lepton number of the electron and electron neutrino? |
+1 Le |
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What is the lepton number of the muo and the muon neutrino? |
+1 Lμ |
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Why are strange particles given this name? |
They have a property called strangeness. |
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How are strange particles created? |
Via the strong interaction. |
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When is strangeness conserved? |
Strong interactions. |
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What does the conservation of strangeness mean? |
That strange particles can only be created in pairs. |
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How do strange particles decay? |
Through the weak interaction. |
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Does strangeness have to be conserved in the weak interactions? |
No, it can change by -1, 0 or 1. |
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What do the properties of hadrons depend on? |
The properties of the quarks they are made of. |
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How many quarks are baryons made out of? What about antibaryons? |
Three quarks. Three antiquarks. |
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What is the quark composition of mesons? |
One quark and one antiquark. |
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What are pions made from? |
Combination of up, down, anti-up, anti-down quarks. |
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What are kaons made from? |
Strange quarks, and a combination of all the other quarks. |
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What is the nine possible combinations? |
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Define quark confinement. |
You cannot get a quark by itself. |
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What interaction can change a quark’s character? |
Weak interaction (e.g beta-minus decay) |
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Describe exchange particles. |
How forces interact between two particles - virtual particles. They can only exist for a very short time - long enough to transfer energy, momentum an other properties between the particles in the interaction - and then they are gone. |
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What are all forces in nature cased by? |
Four fundamental forces with their own exchange particles called gauge bosons. |
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What is the gauge boson of the strong force? What particles does it affect? |
Pions, and it affects hadrons only? |
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What is the gauge boson of the electromagnetic force? What particles does it affect? |
Virtual photons, only affects charged particles. |
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What is the gauge boson of the weak force? What particles does it affect? |
W+, W- bosons, affects all types of particles. |
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What about an exchange particle determines the range of the force? |
The size of the exchange particle. |
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What are the drawing rules for Feynman diagrams? |
Incoming particles start at the bottom of the diagram and move upwards - the direction of time points upwards. The baryons are on one side of the diagram and the leptons stay on the opposite. The W bosons carry charge from one side of the diagram to the other - ensuring charges balance. A W- particle going to the left has the same effect as a W+ particle going to the right. |
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Draw the diagram for beta minus decay. N → p + e- + Ve- |
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Draw the diagram for beta plus decay. P - n + e+ + Ve |
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Draw the diagram for electron capture. |
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Draw the diagram for electron-proton collisions. |
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Describe the photoelectric effect. |
If you shine radiation of high enough frequency (above or at threshold frequency) onto the surface of a metal, it would instantly emit electrons. For most metals, the necessary frequency falls in the ultraviolet range. The photoelectrons are emitted with a variety of kinetic energies ranging from zero to some maximum value. The amount of kinetic energy it has depends on the position of the photoelectron. The surface electrons have more kinetic energy. When the electron absorbs enough kinetic energy, the bonds holding the electrons to the metal break and they can be released. Each photon would transfer all its energy to only one specific electron due to the fact that photons can only exist in discrete packs: quanta. |
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Define the intensity of radiation. |
Amount of energy per second hitting an area of the metal. Maximum kinetic energy is unaffected by varying the intensity of radiation. Increasing the intensity results in more photons per second on an area. |
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Give the equation for energy which includes wavelength and speed of light. |
E=hf=hc/λ |
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What is the equation to find the maximum kinetic energy of a photon? |
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Define stopping potential, and give the equation for it. The potential difference needed to stop the fastest moving electrons. |
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When do we say an electron is excited? |
When it goes to an energy level higher than ground state, by gaining a photon. |
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How do electrons move down energy levels? |
By emitting a photon. |
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Define ionisation and ionisation energy. |
When an electron has been removed from an atom. Energy needed to remove an electron from the ground state atom. |
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Define how fluorescent tubes work in terms of photon emission. |
Fluorescent tubes use the excitation of electrons and photons to produce visible light. They contain mercury vapour, across which a high voltage is applied. This high voltage accelerates fast-moving free electrons which ionise some of the mercury atoms, producing more free electrons. When this flow of free electrons collides with electrons in mercury atoms, the atomic mercury electrons are excited to a higher energy level. When these excited electrons de-excite and return to their ground states, they lose energy by emitting high-energy photons in the UV range. The photons emitted have a range of energies and wavelengths that correspond to the different transitions of electrons. A phosphor coating on the inside of the tube absorbs these photons, exciting its electrons to much higher energy levels. These electrons then cascade down the energy levels and lose energy by emitting many lower energy photons of visible light. |
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How do you get a line spectrum? What does it look like? |
By splitting the light from a fluorescent tube with a prism or a diffraction grating. It is seen as a series of bright lines against a black background. Each line corresponding to a particular wavelength of light emitted by the source. |
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How do diffraction gratings and prisms work? |
By diffracting light of different wavelengths at different angles. |
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What does the line spectra provide evidence for? |
That the electrons in atoms exist in discrete energy levels. Atoms can only emit photons with energies equal to the difference between two energy levels. Since only certain photon energies are allowed, you only see the corresponding wavelengths in the line spectrum. |
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Describe continuous spectra. |
The spectrum of white light is continuous. If you split the light up with a prism, all the colours merge into each other - no gaps. Hot things emit a continuous spectrum in the visible and infrared spectrum. All wavelengths are allowed because the electrons are not confined to energy levels in the object producing the continuous spectrum. The electrons aren’t bound to atoms, they’re free. |
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When do you get a line absorption spectrum and why? |
When a continuous spectrum of energy (white light) passes through a cool gas. At low temperatures, most of the electrons in the gas atoms will be in their ground states. Photons of the correct wavelength are absorbed by the electrons to excite them to higher energy levels. These wavelengths are then missing from the continuous spectrum when it comes out the other side of the gas. You see a continuous spectrum with black lines in it corresponding to the absorbed wavelengths. You see a continuous spectrum with black lines in it corresponding to the absorbed wavelengths. |
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What happens when you compare the line absorption spectra and the emission spectra? |
The line in the absorption spectrum match up to the bright lines in the emission spectrum. The lines are in the same places because the energy differences of the electron transitions that cause them are the same. The photons that cause each line will have the same energy and therefore the same wavelength. |
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Define diffraction. |
When a beam of light passes through a narrow gap, it spreads out. |
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Explain how diffraction is possible (wave-particle duality) |
It can only be explained using waves, if light was acting as a particle, the light particles in the beam would either not get through the gap, or they would pass straight through and the beam would be unchanged. |
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Who proposed Wave-particle duality? |
Louis de Broglie. |
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Give the wave-particle duality equation that de Broglie proposed. |
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How can diffraction patterns be observed? |
Using an electron diffraction tube. Electrons are accelerated to high velocities in a vacuum and then passed through a graphite crystal. As the pass through the spaces between the atoms of the crystal, they diffract just like the waves passing through a narrow slit and produce a pattern of rings. This provides evidence that electrons have wave properties which supports the Broglie’s theory. |
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How do electron microscopes work? |
Shorter wavelength gives smaller diffraction effects. This fact is used in the electron microscope. Diffraction effects blur detail on an image. If you want to resolve tiny detail in an image, you’d need shorter wavelengths. Light blurs out detail more than electron waves do, so an electron microscope can resolve finer detail than a light microscope, allowing you to look at tiny things such as a strand of DNA. |
