Foundation Physics

Front 1

Photoelectric Effect

Back 1

the ejection of electrons from the surface of metals when light is incident on it. The escaping electrons are called photoelectrons

Front 2

Photon

Back 2

Electromagnetic waves of frequency f are emitted and absorbed in quanta of energy, E=hf, called photons.

Front 3

Work function, Φ

Back 3

The minimum amount of energy required to remove a free electron from the surface of a material. Φ = hf(0)

Front 4

Ionisation Energy

Back 4

The minimum amount of energy needed to remove an electron from an atom.

Front 5

Photoelectric equation

Back 5

A measure of the maximum kinetic energy of the electrons emitted as a result of the photoelectric effect. hf=Φ+Ek

Front 6

Stopping Potential

Back 6

The minimum frequency f(0) required to cause photoemission from a metal of work function hf(0). E=qV

Front 7

Binding Energy

Back 7

Nuclear binding energy is the energyrequired to split the nucleus of an atom into its component parts. These parts are called nucleons. E=mc(squared)

Front 8

Nuclear Fission

Back 8

A nuclear process in which a heavy nucleus is split into lighter fragments of approximately equal mass, losing mass and releasing energy in the process. E.g Power plants

Front 9

Nuclear Fusion

Back 9

A nuclear process in which two or more nuclides of low mass number fuse into a nuclide of higher mass number, releasing energy in the process. E.g Fusion of hydrogen to helium in the sun.

Front 10

Radioactivity

Back 10

The spontaneous and random disintegration of an unstable nucleus into a more stable one by emitting alpha-particle, beta-particle and/ or gamma radiation.

Front 11

Half-life

Back 11

The expected time taken for half the number of radioactive nuclei present to decay in a sample. T1/2 = ln2/λ

Front 12

Spontaneous Emission

Back 12

A photon is emitted randomly and in any direction without any external stimulation

Front 13

Stimulated Emission

Back 13

An incoming photon, whose energy is exactly equal to the difference between two energy levels, induces the excited atom to fall into a lower energy level and releases a photon in the process. hf=Energy 2 - Energy 1

Front 14

Population Inversion

Back 14

When there are more atoms in the excited state than in the ground state.

Front 15

Stimulated Absorption

Back 15

When an atom at a lower energy level absorbs a photon and moves to a higher energy level.

Front 16

Magnetic Flux density, B

Back 16

The strength of a magnetic field. Defined as the force of one newton to act on a current of one ampere in a wire of length one metre which is perpendicular to the magnetic field. B=F/ILsinθ

Front 17

Electric Field

Back 17

The electric force per unit charge.

Front 18

Magnetic Flux Linkage

Back 18

A coil of N turns of cross section A is placed in a magnetic field of flux density B with its axis along the field, has a flux linkage of Ф = N Ф = BAN

Front 19

Gravitational potential, Vg

Back 19

The gravitational potential Vg, at a point in a gravitational field is defined as the work done per unit mass in bringing a small object from infinity to that point. Vg = -GM/r. Energy potential = -GMm/r

Front 20

Coulomb’s Law of Electrostatic Force

Back 20

The electrostatic force F between two point charges Q1 and Q2 is directly proportional to the product of the charges and inversely proportional to the square of the distance r between them. F=kQq/r(squared)

Front 21

Electric Field of Force

Back 21

A region of space in which a charge experiences a force due to electrical effect of another charge.

Front 22

Electric field strength

Back 22

The electric field strength E at a point P in an electric field is defined as the force experienced per unit +ve charge placed at that point. E=F/Q (unit NC-1)

Front 23

Electric Potential, V

Back 23

The electric potential V at a point in an electric field is defined as the work done per unit positive charge by an external agent to move a charge from infinity to that point. Ve = kQ/r (unit JC-1). Energy potential = kQq/r (unit J)

Front 24

Gravitational potential energy

Back 24

The gravitational potential energy of a mass, m, placed at a point in the gravitational field is defined as the work done in bringing it from infinity to that point.

Front 25

Gravitational potential, Φ

Back 25

The gravitational potential, Φ, at a point in a gravitational field is defined as the work done per unit mass in bringing a test mass from infinity to that point.

Front 26

Gravitational field strength, g

Back 26

The gravitational field strength, g, at a point is the gravitational force per unit mass acting on a small mass at that point. g=F/m. g= -GM/r(squared)

Front 27

Gravitational field

Back 27

The gravitational field is a region where a gravitational force is experienced by another mass placed in it.

Front 28

Newton’s Law of Gravitation

Back 28

Every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them. F= - GMm/r(squared)

Front 29

Diffraction

Back 29

Diffraction is the spreading of waves when they pass through an opening or around an obstacle.

Front 30

Coherence

Back 30

Two waves are coherent when the phase difference between them is constant. They should have the same frequency and wavelength and approx the same amplitude.

Front 31

Path Difference

Back 31

the difference between the distances travelled by two waves.

Front 32

Interference

Back 32

A resulting oscillation when a periodic driving force is applied to a system.

Front 33

Principle of Superposition

Back 33

When 2 or more waves meet, the resultant wave is equal to the vector sum of the individual displacements at that instant and position.

Front 34

Root Mean Square

Back 34

The root-mean-square of an alternating current (or voltage) is defined as that value of steady direct current (or voltage) which would dissipate energy at the same rate in a given resistance.

Front 35

Electromotive force

Back 35

E.m.f is defined as the energy converted from other forms into electrical energy by a source in driving a unit charge round a complete circuit.

Front 36

Potential Difference

Back 36

1 volt is the potential difference between two points in a circuit when 1 Joule of work is done moving 1 coulomb of charge between two points. p.d.=energy/charge

Front 37

Wavelength, λ

Back 37

The distance, measured in the direction of propagation of a wave, between two successive points in the wave that are characterized by the same phase of oscillation. v=f λ

Front 38

Amplitude, A

Back 38

The magnitude of the maximum displacement of a particle from its equilibrium position.

Front 39

Critical Damping

Back 39

Critical damping is where the system, when displaced and released, returns to equilibrium, withing one complete oscillation.

Front 40

Angular velocity

Back 40

The rate of change of angular displacement per unit time. v=rω

Front 41

Angular displacement

Back 41

The angle in radians through which a point of line has been rotated in a specific sense about an axis. s=rθ

Front 42

Damping

Back 42

The process whereby dissipative forces act to remove energy from an oscillating system, causing the amplitude of oscillation to decrease with time.

Front 43

Simple Harmonic Motion

Back 43

An oscillatory motion in which the object’s acceleration is directly proportional to its displacement from equilibrium AND is always directed towards the centre of oscillation.

Front 44

Polarization

Back 44

The process by which the oscillations of a wave are made to occur in one direction only.

Front 45

Stationary waves

Back 45

They are the result of the superposition of two waves of similar amplitude, frequency and plane travelling in opposite directions. They do not transfer energy along the direction of travel

Front 46

Intensity

Back 46

The intensity of a wave motion at a point is defined as the power per unit area incident normally to the surface at that point.

Front 47

Phase difference

Back 47

The fraction of one cycle by which one wave moves behind the other. For t=0 at equlibrium, s=Asin(2πft). For t=0 at max displacement (A) s=Acos(2πft)

Front 48

Frequency, f

Back 48

Measured in Hz. The number of complete cycles of the oscillation each second. f=1/T

Front 49

Period, T

Back 49

Time taken for one complete oscillation.

Front 50

Standing Wavelength

Back 50

The wavelength of a standing wave is twice the distance between two nodes or between two antinodes.

Front 51

Centripetal Force

Back 51

A force which acts on a body moving in a circular path and is directed towards the centre around which the body is moving. Fcentripetal = mv(squared)/r

Front 52

Centripetal Acceleration

Back 52

The rate of change of tangential velocity. acentripetal= v(squared)/r

Front 53

Time taken to move once round a circular path:

Back 53

T=2πr/v

Front 54

Speed in orbit. (satellites)

Back 54

v(squared) = 4π(squared)R(squared)/T(squared)

Front 55

Energy in orbit. (satellites)

Back 55

Etotal= -GMm/r + (1/2) GMm/r

Front 56

Refraction

Back 56

Bending of a wave caused by a change in its speed, as it passes from one material to another.

Front 57

Uniform Circular Motion

Back 57

Refers to an object travelling at a constant speed on a circular path.

Front 58

Angular Velocity

Back 58

The rate of change of angular displacement per unit time.

Front 59

Hooke’s Law

Back 59

Within its limit of proportionality, the applied force, F, on a spring is directly proportional to its extension, x. F= -kx

Front 60

Systematic Errors

Back 60

An error that causes the results to be always higher or always lower than the true value

Front 61

Random Errors

Back 61

An error that causes irregularities in the experiment, resulting in readings that are scattered about the true value.

Front 62

Magnetic Flux

Back 62

The 'amount of field' i.e. The product of the uniform magnetic field times by the perpendicular area that it penetrates. Φm=BA

Front 63

Lenz's Law

Back 63

If an induced e.m.f flows, its direction is always such that it will oppose the change which produced it. Obeys Newton's 3rd Law, the conservation of energy.

Front 64

Faraday's Law

Back 64

The magnitude of the induced electromotive force is directly proportional to the rate of change of flux linkage.

Front 65

Snell's Law

Back 65

Refractive index going from material 1 to material 2. n = sin i/sin r = c1/c2

Front 66

Focal point, F

Back 66

The focal point of a converging lens is the point where light from a very distant point object is brought to focus by the lens.

Front 67

Focal length, f

Back 67

The focal length f of a thin lens is the distance from the centre of the lens to F, the focal point

Front 68

Power of a lens

Back 68

Measured in dioptres, where f is the focal length in metres. P=1/f

Front 69

Lens equation

Back 69

Curvature after lens is equal to the curvature before plus the curvature added. 1/v=1/u + 1/f

Front 70

Linear magnification

Back 70

The ratio of the height or length of the image to the height or length of the object viewed directly. magnification = height of image/height of object. m=v/u

Front 71

Angular frequency

Back 71

ω= 2πf

Front 72

Acceleration for SHM

Back 72

a= -(2πf)(squared)s. At max acceleration replace s with A.

Front 73

Velocity for SHM

Back 73

Max velocity at the centre. vmax= (2πf)A

Front 74

Energy in a harmonic oscillator

Back 74

Etotal=1/2mv(squared) + 1/2 ks(squared)

Front 75

Progressive waves

Back 75

They propagate through space or through a substance. They transfer energy along the direction of travel.

Front 76

Nodes

Back 76

A position of minimum amplitude on a standing wave.

Front 77

Antinodes

Back 77

A position of maximum amplitude on a standing wave.

Front 78

Harmonics (Open end)

Back 78

First harmonic(fundamental): f1 = v/2L

Second harmonic(1st overtone): f2 = 2*v/2L

Third harmonic(2nd overtone): f3 = 3*v/2L

Front 79

Harmonics (Closed end)

Back 79

First harmonic: f1 = v/4L

Third harmonic: f3 = 3*v/4L

Fifth harmonic: f5 = 5*v/4L

Front 80

Huygens' wavelets

Back 80

The theory considers each point on a wavefront as a secondary emitter of wavelets. The wavelets from the points along a wavefront create a new wavefront, so that the wave propagates.

Front 81

Phasors

Back 81

Phasors are used to represent amplitude and phase in a wave. A phasor is a rotating arrow used to represent a sinusoidally changing quantity.

Front 82

Young's double slit experiment

Back 82

Calculate wavelength: λ = dx/L

Intensity minima: dsinθ = nλ [Bright fringes]

dsinθ = (n+1/2)λ [Dark fringes]

(d, gap width; n is a positive integer)

Front 83

Transverse waves

Back 83

A wave in which the motion of the medium is a right angles to the direction of the wave. e.g Light and EM waves.

Front 84

Flemming's left hand rule

Back 84

thuMb - Motion

First finger - Field

seCond finger - Current

Front 85

Maxwell's right hand rule

Back 85

Finger of right hand curls with current; thumb shows direction of magnetic field.

Front 86

Force on a conductor in a magnetic field.

Back 86

When the conductor is placed at right angles to the magnetic field, a force is experienced by the conductor. F=BIL

Front 87

Definitions of moving charges

Back 87

q=It. If the charge is moving with velocity v, then the distance it travels in time t is L=vt.

F=Bqv (Bev for an electron)

Front 88

Capacitance

Back 88

Charge stored per unit potential difference. C=Q/V. Unit; 1 Coulomb per volt - Farad (F)

Front 89

Time Constant (Capacitance)

Back 89

The time taken for the voltage or charge to drop 37% of its original value.

Front 90

Activity (Nuclear Physics)

Back 90

The number of radioactive decays per unit time. Unit = Becquerels. A= -λN = A0e^-λt

Front 91

Radioactivity equation

Back 91

N= N0e^-λt

N= no. remaining after time t

N0= original number present

t = time λ= decay constant

[time constant = 1/λ]

Front 92

Proton Number - Nucleon Number

Back 92

Proton Number, Z - The number of protons in a nucleus.

Nucleon Number, A - The number of nucleons(protons + neutrons) in any nucleus.

Front 93

Isotopes

Back 93

Two nuclides (a nucleus with a distinct number of protons and neutrons) with thesame number of protons but different numbers of neutrons.

Front 94

Graphing P.D./Charge. Energy stored.

Back 94

V=E/Q Energy = p.d x charge (the area beneath the graph). Remember area of triangle: 1/2 (V0Q0) This is the energy stored in a capacitor

Front 95

Kirchoff's 1st Law

Back 95

At any junction in a circuit, the sum of the currents arriving at the junction = the sum of the currents leaving the junction. The sum of the currents at a junction is zero. ΣI=0

Front 96

Kirchoff's 2nd Law

Back 96

In any loop (path) around a circuit, the sum of the emfs = the sum of the pds. ΣE=ΣIR

Front 97

Alternating current

Back 97

An electric current that repeatedly reverses its direction, usually at a constant frequency. In 1 cycle, current/p.d reverses from its peak value in 1 direction to its peak value in the other and back again.

Front 98

Root mean square (rms) [A.C.]

Back 98

The r.m.s. value of an a.c. supply is the steady d.c. which would convert electrical energy to thermal energy at the same rate in a given resistance. V=V0/root:2 (same for I)

Pmean=Irms*Vrms

Front 99

Inductor [A.C.]

Back 99

A passive two-terminal electrical component which resists changes in electric current passing through it. When a current flows through it it stores energy temporarily in a magnetic field. XL = 2πfL (ohms)

Front 100

Henries (H)

Back 100

An inductor (L) has an inductance of 1H if a rate of change of current 1As-1 through it produces an e.m.f. of 1 volt across it.

Front 101

Capacitor [A.C.]

Back 101

For a.c. circuits, the cell appears to be constantly charging due to the change in direction of the current. But the capacitor does offer opposition; this is called reactance. XC = 1/2πfC

Front 102

Transformer [A.C.]

Back 102

Changes the peak voltage of an alternating potential difference. Rule: Vp/Vs=Np/Ns.

N=number of turns on coil. V=p.d

Assuming 100% efficiency, IpVp=IsVs

Front 103

Resonance

Back 103

Resonance occurs when a source of energy oscillates at the same frequency as the natural frequency of a structure.

Front 104

Electromotive force (e.m.f.)

Back 104

the energy provided by a cell or battery per coulomb of charge passing through it, it is measured in volts (V)