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OCR Physics A-level > Definitions For Paper 2 > Flashcards

Definitions For Paper 2 Flashcards

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1
Q

Absorption coefficient

A

A measure of the absorption of x-ray photons by a substance also known as as attentiuon coefficient

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2
Q

Acoustic matching

A

The use of two substances with similar acoustic impedance to minimise reflection of ultrasound at the boundary between them

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3
Q

Activity

A

The rate of which nuclei decay or disintegrate in a radioactive source measured in becquerels

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4
Q

Acoustic impedance

A

The product of the density of a substance and the speed of ultrasound in that substance

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5
Q

Alpha radiation

A

Ionising radiation consisting of particles comprising two protons and two neutrons with a charge of +2e

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6
Q

Ampere

A

The current flowing in two parallel wires in a vacuum 1m apart such that there is an attractive force of 2x10^-7N per metre length of wires between them

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7
Q

Amplitude

A

The maximum displacement from the equilibrium position

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8
Q

Angle of incidence

A

The angle between the direction of travel of an incident wave and the normal at a boundary between two media

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9
Q

Angle of reflection

A

The angle between the direction of travel of a reflected wave and the normal at a boundary between two media

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10
Q

Anion

A

A negatively charged ion, one which is attracted to an anode

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11
Q

Annihilation

A

The complete destruction of a particle and its antiparticle in an interaction that releases energy in the form of identical photons

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12
Q

Anode

A

A positively charged electrode

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13
Q

Antiparticle

A

The antimatter counterpart of a particle with the opposite charge to the particle and exactly the same rest mass

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14
Q

Antiphase

A

Particles oscillating completely out of step with each other

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15
Q

Atomic mass unit

A

One atomic mass unit is one-twelfth the mass of a neutral carbon-12 atom

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16
Q

Atomic number

A

The number of protons in a nucleus Z

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17
Q

Attenuation

A

The decrease in the intensity of electromagnetic radiation as it passes through matter and/or space

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18
Q

Attenuation coefficient

A

A measure of the absorption of x-ray photons by a substance also known as absorption coefficient - m^-1

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19
Q

Background radiation

A

The radiation emitted by the surroundings, which must be measured before radiation produced in an experiment can be usefully measured

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20
Q

baryon

A

Any hadron made with a combination of three quarks

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21
Q

Battery

A

A collection of cells that transfers chemical energy into electrical energy

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22
Q

Becquerel

A

One becquerel is an activity of one decay per second

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23
Q

Beta decay (B-)

A

A neutron in an unstable nucleus decays into a proton, an electron and and electron antineutron

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24
Q

Beta decay (B+)

A

A proton in an unstable nucleus decays into a neutron, a positron and an electron neutrino

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25
Q

Beta radiation

A

Ionising radiation consisting of fast-moving electrons (B- or B+) emitted from unstable nuclei with a charge of -e or +e

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26
Q

Binding energy

A

The minimum energy required to completely separate a nucleus into its constituent protons and neutrons

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27
Q

Binding energy per nucleon

A

The binding energy divided by the number of protons and neutrons in the nucleus; the greater the binding energy per nucleon the more tightly bound are the nucleons within the nucleus

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28
Q

Capacitance

A

The charge stored per unit potential difference across a capacitor

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29
Q

Capacitor

A

A component that stores charge, consisting of two plates plates separated by an insulator

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30
Q

Carbon dating

A

A method of determining they age of organic material, by comparing the activities or the ratios of carbon-14 to carbon-12 nuclei of the dead material of interest and similar living material

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31
Q

Cathode

A

A negatively charged electrode

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32
Q

Cation

A

A positively charged ion, one which is attracted to a a cathode

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33
Q

Cell

A

A device that transfers chemical energy into electrical energy

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34
Q

Chain reaction

A

A reaction in which the neutrons from an earlier fission stage are responsible for future fission reactions leading to an exponential growth in the rate of the reactions

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35
Q

Charge carriers

A

A particle with charge that moves through a material to form an electric current

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36
Q

Cloud chamber

A

A detector of ionising radiation consisting of a chamber filled with air saturated with vapour at a very low temperature so that droplets of liquid condense around ionised particles left along the path of radiation

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37
Q

Coherence

A

Two waves sources or waves that are coherent have a constant phase difference

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38
Q

Collimator

A

Part of a gamma camera, a honeycomb of long thin tubes made from lead that absorbs any photons arriving at an angle to the axis of the tubes so that a clear picture is obtained

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39
Q

Compression

A

A moving region in which the medium is denser or has higher pressure than the surrounding medium

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40
Q

Conservation of charge

A

A conservation law which states that electric charge can neither be created more destroyed - the total charge in any interaction must be the same before and after the interaction

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41
Q

Constructive interference

A

Superposition of two waves in phase so that the resultant wave has greater amplitude than the original waves

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42
Q

Control rods

A

Rods made of a material whose nuclei readily absorb neutrons which can be moved into or out of a reactor core to ensure that exactly one slow neutron survives per fission reaction or to completely stop the fission reaction

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43
Q

Conventional current

A

A model used to describe electric current in a circuit - conventional current travels from positive to negative - it is the direction in which positive charges would travel

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44
Q

Coolant

A

Substance that removes the thermal energy produced from reactions within a fission reactor

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45
Q

Corrected count rate

A

The radiation count rate measured in an experiment minus the background count rate

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46
Q

Coulomb

A

SI unit of electrical charge - 1 coulomb of electric charge passes a point in one second when there is an electric current of one ampere

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47
Q

Coulomb’s law

A

Any two point charges exert an electrostatic force on each other that is directly proportional to the product of their charges and inversely proportional to the square of their separation

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48
Q

Coupling gel

A

A gel with acoustic impedance similar to that of skin smeared onto the transducer and the patients skin before an ultrasound scan in order to fill air gaps and ensure that almost all the ultrasound enters he patients body

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49
Q

Critical angle

A

The angle of incidence at the boundary between two media that will produce an angle of refraction of 90 degrees

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50
Q

Crystallography

A

A method of determining the structure of a substance by studying the interference patterns produced by waves passing through a crystal of the substance

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51
Q

Daughter nucleus

A

A new nucleus formed following a radioactive decay

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52
Q

De broglie equation

A

An equation relating the wavelength and momentum of a particle

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53
Q

Decay constant

A

The probability of decay of an individual nucleus per unit time

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54
Q

Density

A

The mass per unit volume of a substance

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55
Q

Destructive interference

A

Superposition of two waves in antiphase so that the waves cancel each other out and the resultant wave has smaller amplitude than the original waves

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56
Q

Diffraction

A

The phenomenon in which waves passing through a gap or around an obstacle spread out

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57
Q

Diffraction grating

A

A glass or plastic slide on which as many as 1000 lines in a millimetre are ruled at a spacing that diffracts visible wavelengths of light

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58
Q

Diode

A

A semiconductor component that allows surrender only in one particular direction

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59
Q

Displacement

A

He distance from the equilibrium position in a particular direction - displacement is a vector can be positive or negative

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60
Q

Electric charge

A

A physical property either positive or negative measured in coulombs or as a relative charge

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61
Q

Electric current

A

The rate of flow of charge measured in ampere: normally a flow of electrons in metals or. A flow of ions in electrolytes

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62
Q

Electric field strength

A

The force experienced per unit positive charge at the point

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63
Q

Electric potential

A

The work done by an external force per unit positive charge to bring a charge from infinity to a point in an electric field

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64
Q

Electric potential difference

A

The work done by an external force per unit positive charge to move a charge between two points in an electric field

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65
Q

Electromagnetic spectrum

A

The full range of frequencies of electromagnetic eaves , from gamma rays to radio waves

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66
Q

Electrolyte

A

A liquid containing ions that are free to move and so to conduct electricity

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67
Q

electromagnetic wave

A

Transverse waves with oscillating electric and magnetic field components such as light and X-rays that do not need a medium to propagate they travel at a speed of light 3x10^8 ms^-1 in a vacuum

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68
Q

Electromotive force

A

The energy transferred from chemical to electrical energy per unit charge

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69
Q

Electron gun

A

A device that uses a large accelerating potential difference to produce narrow beam of electrons

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70
Q

Electronvolt

A

A derived unit of energy used for subatomic particles and photons
- the energy transferred to or form an electron whin it passes through potential difference of 1 volt = 1eV

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71
Q

Elementary charge

A

The electric charge equivalent to the charge on a proton = e

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72
Q

Elementary particle

A

A fundamental particle

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73
Q

Energy

A

The capacity for doing work - J

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74
Q

Equation of state of an ideal gas

A

pV = nRT, where n is the number of moles of gas

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75
Q

Equilibrium position

A

The resting position of waves or particles in an oscillation

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76
Q

Exponential decay

A

A constant-ratio process in which a quantity decreases by the same factor in equal time intervals

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77
Q

Extension

A

The increase in length of an object when a tensile force is exerted on it

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78
Q

Faraday’s law

A

The magnitude of the induced e.m.f is directly proportional to the rate of change of magnetic flux linkage

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79
Q

Filament lamp

A

An electrical component containing a narrow filament of wire that transfers electrical energy into heat and light

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80
Q

Fission

A

A process in which a large nucleus splits into two smaller nuclei after absorbing a neutron

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81
Q

Flemings left hand rule

A

A mnemonic for the direction of the force experienced by a current-carrying wire placed perpendicular to the external magnetic field: on the left hand, the fist finger gives the direction of the external magnetic field, the second finger gives the direction of the conventional current and the thumb gives the direction of motion in the wire

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82
Q

Free electron

A

An electron in a kernel that s not bound to an ton and is free to move - delocalised electron

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83
Q

Frequency

A

The number of wavelengths passing a given point per unit time

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84
Q

Fundamental frequency

A

The lowest frequency at which an object can vibrate

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85
Q

Fundamental mode of vibration

A

A vibration at the fundamental frequency

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86
Q

Fundamental particle

A

A particle that has no internal structure and hence cannot be split into smaller particles

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87
Q

Fusion

A

A process in which two smaller nuclei join together to form one larger nucleus

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88
Q

Gamma radiation

A

Ionising radiation consisting of high-energy photons with wavelengths less than about 10^-13m

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89
Q

Gamma rays

A

Short-wavelength electromagnetic waves with wavelengths from 10^-10m to 10^-16m

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90
Q

Gold-leaf electroscope

A

A device with a metallic stem and a gold leaf that can be used to identify and measure electric charge

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91
Q

Hadron

A

A particle or antiparticle that is affected by the strong nuclear force and if charged by the electromagnetic force

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92
Q

Half-life

A

The average time it takes for half the number of active nuclei in a sample of an isotope to decay

93
Q

Harmonic

A

A whole-number multiple of the fundamental frequency

94
Q

Impedance matching

A

The use of two substances with similar acoustic impedance to minimise reflection of ultrasound at the boundary between them

95
Q

In phase

A

Particles oscillating perfectly in time with each other (max displacement at the same time) are in phase

96
Q

Induced fission

A

Nucleus fission occurring when a nucleus becomes unstable on absorbing another particle

97
Q

Infrared waves

A

Electromagnetic waves, with wavelengths from 10^-3m to 7x10^-7m

98
Q

Intensity

A

The radiant power passing through a surface per unit area unit Wm^-2

99
Q

Intensity reflection coefficient

A

The ratio of reflected intensity over incident intensity for ultrasound incident at a boundary

100
Q

Interference

A

Superposition of two progressive waves from coherent sources to produce a resultant wave with a displacement equal to the sum of the individual displacements from the two waves

101
Q

Interference pattern

A

A pattern of constructive and destructive interference formed as waves overlap

102
Q

Internal resistance

A

The resistance of a source of e.m.f due to its construction which causes a loss in voltage as the charge passes through the source

103
Q

Ion

A

An atom that has either lost or gained electrons and so has a net charge

104
Q

Ionic solution

A

An ionic compound dissolved in a liquid to form an electrolyte

105
Q

Ionising radiation

A

Any form of radiation that can ionise atoms by removing an electron to leave a positive ion

106
Q

Isotopes

A

Nuclei of the same element that have the same atomic number (protons) but different nucleon numbers (neutrons)

107
Q

I-V characteristic

A

A description of the relationship between the electric current in a component and the potential difference across it - graph

108
Q

Kilowatt-hour

A

A derived unit of energy - paying for electrical energy

109
Q

Kirchoff’s first law

A

At any point in an electrical circuit the sum of currents into that point is equal to the sum of currents out of that point

110
Q

Kirchoffs second law

A

In a closed loop of an electrical circuit the sum of e.m.f.s is equal to the sum of the p.d.s

111
Q

Law of reflection

A

The angle of incidence is equal to the angle of reflection

112
Q

Lepton

A

A fundamental particle or antiparticle that is not affected by the strong nucleus force - an electron

113
Q

Light-dependent resistor

A

An electrical component with a resistance that decreases as the light intensity incident on it increases

114
Q

Light-emitting diode

A

A type of diode hat emits light when it conducts electricity

115
Q

Loading

A

Connecting a component or a device across the terminals of a source of e.m.f. Or across another component

116
Q

Longitudinal wave

A

A wave in which the medium is displaced in the same line as the direction of energy transfer - oscillations of the medium particles are parallel to the direction of the wave travel

117
Q

Lost volts

A

The potential difference across the internal resistor of a source of e.m.f

118
Q

Magnetic flux

A

The product of the component of the magnetic flux density perpendicular to a given area and the cross-sectional area

119
Q

Magnetic flux density

A

The strength of a magnetic field defined by the equation F/IL

120
Q

Lenz’s law

A

The direction of the induced e.m.f. Is always such to oppose the change producing it

121
Q

Magnetic flux linkage

A

The product of the number of turns in a coil and the magnetic flux

122
Q

Mass defect

A

The difference between the mass of a nucleus and the mass of its completely separated constituent nucleons

123
Q

Maximum (waves)

A

The point of greatest amplitude in an interference pattern produced by constructive interference

124
Q

Medical tracer

A

A radiopharmaceutical - a compound labelled with a radioisotope that vanishes be traces inside the body with a gamma camera

125
Q

Meson

A

Any hadron comprising a combination of a quark and an anti-quark

126
Q

Microwaves

A

Long-wavelength electromagnetic waves 10^-1m to 10^-3 m

127
Q

Minimum (waves )

A

The point of least amplitude in an interference pattern produced by destructive interference

128
Q

Moderator

A

A substance used to slow down the fast neutrons produced in fission reactions so that they can propagate the fission reaction

129
Q

Monochromatic light

A

Light of a single frequency

130
Q

Negative (charge)

A

One tube of electric charge - attract positive charges and repel negative charge

131
Q

Neutrino

A

A lepton (fundamental particle) that carried no charge and may have a tiny mass.

132
Q

Neutron

A

An electrically neutral particle (hadron) found in the nuclei’s of atoms

133
Q

Node

A

For a stationary wave, a point where the amplitude is always zero

134
Q

Non-ohmic component

A

A component that does not obeys ohms law e,a filament lap and diode

135
Q

Normal

A

An imaginary line perpendicular to a surface such as the boundary between one medium to another

136
Q

Nucleon

A

A particle in the nucleus of an atom either a proton or a neutron

137
Q

Nucleon number

A

Te total number of protons and neutrons in a nucleus - A

138
Q

Nucleus

A

The small, positively charged region at the centre of an atom where most of the mass of the atoms is concentrated

139
Q

Number density

A

The number of free electrons per cubic metre of material - n and unit = m^-3

140
Q

Ohm

A

The derived SI unit if resistance - the resistance of a component has a potential difference of 1V per ampere

141
Q

Ohm’s law

A

The potential difference across a conductor is directly proportional to the current in the component as long as its temperature remains constant

142
Q

Ohmic conductor

A

A conductor that obeys ohm’s law

143
Q

Optical fibre

A

A fibre made of glass designed with a varying refractive index in order to totally internal reflect pulses of visible or infrared light travelling through it

144
Q

Oscilloscope

A

An instrument that displays n electrical signal as a voltage against time trace on screen

145
Q

Out of phase

A

Particles are neither in phases nor antiphase

146
Q

Pair production

A

The replacement of a single photon with a particle and a corresponding antiparticle of the same total energy

147
Q

Parallel circuit

A

A type of branching electrical circuit in which there is more than one path for the current - components In parallel have the same potential difference

148
Q

Parent nucleus

A

A nucleus before the occurrence of radioactive decay

149
Q

Partially polarised

A

Description of a transverse wave in which there are more oscillations in one particular plane but the wave is not completely plane polarised - transverse waves reflect off a surface

150
Q

Path difference

A

The difference in the distance travelled by two waves from their source to a specific point

151
Q

Peak

A

The maximum positive amplitude of a transverse wave

152
Q

Period

A

The time taken for one complete wavelength to pass a given point

153
Q

Phase difference

A

The difference between the displacements of particles along a wave

154
Q

Photoelectric effect

A

The emission of photoelectrons from a metal surface when electromagnetic radiation above a threshold frequency is incident on the metal

155
Q

Photoelectrons

A

Electrons emitted from the surface of a metal by the photoelectric effect

156
Q

Photomultiplier tube

A

An apparatus that converts a photon of visible light into an electrical pulse - part of gamma camera

157
Q

Photon

A

A quantum of electromagnetic energy - E=hf

158
Q

Piezoelectric effect

A

The production of an electromotive force by some crystals, such as quartz, when they are compressed, stretched, twisted or distorted

159
Q

Plane polarised

A

A transverse wave in the oscillations are limited to only one plane

160
Q

Polycrystalline graphite

A

Thin layers of graphite with regularly arranged carbon atoms in different orientations

161
Q

Positive (charge)

A

One type of electric charge - attract negative charges and repel positive charges

162
Q

Positron

A

The antiparticle of the electron

163
Q

Potential difference

A

The energy transferred from electrical energy to together forms per unit charge

164
Q

Potential divider

A

An electrical circuit designed to divide the potential difference across two or more components in order to produce a specific output

165
Q

Potentiometer

A

An electrical component with three terminals and some form sliding contact that can be adjusted to vary the potential difference between two of the terminals

166
Q

Principle of superposition of waves

A

When two similar types of waves meet at a point the resultant displacement at that point us equal to the sum of the displacements of the individual waves

167
Q

Progressive waves

A

A wave in which the peaks and troughs, or compressions and rare fractions, move through the medium as energy is transferred

168
Q

Proton

A

A positively charges particle (hadron) found in the nucleus of atoms

169
Q

Proton number

A

The atomic number the number of protons in a nucleus -Z

170
Q

P-waves

A

Primary waves - longitudinal waves that travel through the earth from an earthquake

171
Q

Quark

A

An elementary particle that can exist is 6 forms and joins with other quarks to form hadrons

172
Q

Quantisation

A

The availability of some quantities such as energy or charge

173
Q

Radial field

A

A symmetrical field that diminishes with distance^2 from its centre (gravitational field around a spherical mass) (electrical field around a spherical charged object)

174
Q

Radioactivity

A

The process by which unstable nuclei split or decay emitting ionising radiation

175
Q

Radiopharmaceutical

A

A radioisotope chemically combined with elements that will target tissues in order to ensure that the radioisotope reaches the correct organ or tumour for diagnosis or treatment

176
Q

Radio waves

A

Long-wavelength electromagnetic waves, wavelength greater than 10^-1m

177
Q

Rarefraction

A

A moving region in which the medium is less dense or has less power than the surrounding medium

178
Q

Ray

A

A line representing the direction of energy transfer of a wave, perpendicular to the wavefronts

179
Q

Reflection

A

The change in direction of a wave at a boundary between two different media so that the wave remains in the original medium

180
Q

Refraction

A

The change in direction of a wave as it changes speed when it passes from one medium to another

181
Q

Relative charge

A

A simplified measurement of the electric charge of a particle or object measured in multiples of elementary charge

182
Q

Resistance

A

A property of a component calculated by dividing the potential difference across it by the current in it

183
Q

Resistivity

A

A property of a material defined as the product of the resistance of a component made of the material and its cross-sectional area divided by its length

184
Q

Resistor

A

An electrical component that obeys ohm’s law transferring electrical energy to thermal energy

185
Q

Resistor circuit

A

Two or more resistors arranged to provide a specific resistance

186
Q

Right-hand grip rule

A

For a current carrying wire, thumb points in the direction of the conventional current and the direction of the field id given by the direction in which the fingers of the right hand would curl round the wire

187
Q

Scintillator

A

Part of a gamma camera - made of sodium iodide- produces thousands of photons of visible light when struck by a single gamma photon

188
Q

Semiconductor

A

A material with a lower number density than a typical conductor

189
Q

Series

A

An arrangement of electrical components end-to-end that means that the current is the same,e in each component

190
Q

Series circuit

A

A type of electrical circuit where the components are connected end-to-end

191
Q

Standard model

A

The current theory of particle physics that deals with elementary particles (quarks and electrons) and their interactions

192
Q

Standing wave

A

A wave that remains in a constant position with no net transfer of energy and is characterised by its nodes and antinodes

193
Q

Stationary wave

A

A wave that remains in a constant position with non net transfer of energy and is characterised by nodes and antinodes

194
Q

Step-down transformer

A

A transformer with fewer turns on the secondary than on the primary coil and a lower output voltage than input voltage

195
Q

Step-up transformer

A

A transformer with more turns on the secondary than on the primary coil and a higher output voltage than input voltage

196
Q

Strong nuclear force

A

One of the four fundamental forces in nature acting on hadrons and holding nuclei together

197
Q

Superconductivity

A

A phenomenon in which the resistivity of a material fall to almost zero when the material is cooled below a certain temperature

198
Q

Superposition

A

Overlap of two waves at a point in space

199
Q

S-waves

A

Secondary-waves - transverse waves that travel through the earth from an earthquake

200
Q

Target metal

A

A metal with a high melting point used for the anode in an x-ray tube

201
Q

Terminal p.d.

A

The potential difference across an electrical power source - when there is no current this is equal to the e.m.f. of the source but if there is a current in the source this is equal to the e.m.f. minus the lost volts

202
Q

Thermal neutron

A

A neutron in a fission reactor with mean kinetic energy similar to the thermal energy of particles in the reactor core - slow neutron

203
Q

Thermionic emission

A

The emission of electrons from the surface of a heated piece of metal or hot metal wire

204
Q

Thermistor

A

An electrical component that has a resistance that decreases as the temperature increases

205
Q

Threshold frequency

A

The minimum frequency of the electromagnetic radiation that will cause the emission of an electron from the surface of a particular metal

206
Q

Threshold voltage

A

The minimum potential trial difference at which a diode begins to conduct

207
Q

Time constant

A

The product of a capacitance and resistance - regulating to the time taken for the p.d. to decrease to e^-1 of its initial value when the capacitor discharges through a resistor

208
Q

Total internal reflection

A

The reflection of all light hitting a boundary between two media back into the original medium when the light is travelling through the medium with the higher refractive index and the incidence angle art the boundary is greater than the critical angle

209
Q

Transverse wave

A

A wave in which the medium is displaced perpendicular to the direction of energy transfer - the oscillations of medium particles are perpendicular to the direction of travel of the wave

210
Q

Trough

A

The maximum negative amplitude of a transverse wave

211
Q

Ultraviolet

A

Electromagnetic waves with wavelengths form 4x10^-7m to 10^-8m

212
Q

Ultrasound transducer

A

A device used both to generate and ti receive ultrasound which changes electrical energy into sound and sound into electrical energy

213
Q

Unpolarised

A

Description of a transverse wave in which the oscillations occur in many planes

214
Q

Velocity selector

A

A device that used both electric and angelic fields to select charged particles of specific velocity

215
Q

Visible light

A

Electromagnetic waves with wavelengths from 4x10^-7m to 7x10^-7m

216
Q

Volt

A

The derived SI unit of potential difference and electromotive force defined as the energy transferred per unit charge

217
Q

Wave profile

A

A graph showing the displacement of the particle in the wave against the distance along the wave

218
Q

Wave source

A

A source of waves such as light or sound - the object moving relative to an observer of the Doppler effect

219
Q

Wave speed

A

The distance travelled by the wave per unit time

220
Q

Wavefront

A

A line of points in phase with each other in a wave, perpendicular to the direction of energy transfer

221
Q

Wavelength

A

The minimum distance between two points oscillating in phase

222
Q

Wave-particle duality

A

A theory that states that matter has both particle and wave properties ad also electromagnetic radiation has wave and photon nature

223
Q

Weak nuclear force

A

On of the four fundamental forces in nature, responsible for inducing beta-decay within unstable nuclei

224
Q

Work function

A

The minimum energy needed to remove a single electron from the surface of a particular metal

225
Q

X-rays

A

Short wavelength from 10^-8m to 10^-13 m which an be used in medical imaging

226
Q

X-ray tube

A

A piece of equipment that produces x-ray photons by firing electrons form a heated cathode across a large p.d. in an evacuated tube

227
Q

X-ray photons

A

Produced. When the electrons are decelerated by hitting the target metal of an anode

228
Q

Rest mass

A

The mass of an object, such as a particle, when it is stationary

229
Q

Semiconductor

A

A material with a lower number density than a typical conductor

OCR Physics A-level (28 decks)

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