Defenitions Flashcards
(262 cards)
1
Q
Absolute zero
A
The lowest possible temperature
2
Q
Acceleration
A
The rate of change of velocity
3
Q
Accurate result
A
A result that’s really close to the true answer
4
Q
Acoustic impedance
A
The density of a material multiplied by the speed of sound in the material
5
Q
Alpha decay
A
A toe of decay in which an unstable nucleus of an atom emits a helium nucleus
6
Q
Alpha particle
A
A particle formed of two protons and two neutrons (the same as a helium nucleus)
7
Q
Alpha radiation
A
Nuclear radiation made up of alpha particles
8
Q
Alternating current
A
A current that changes with time in a regular cycle
9
Q
Ammeter
A
A component used to measure the current flowing through a circuit
10
Q
Amplitude
A
The maximum displacement of a wave, I.e the distance from the undisturbed position to the crest, or trough
11
Q
Angle of incidence
A
The angle that incoming light makes to the normal of a boundary
12
Q
Absorption line
A
A dark line in the continuous spectrum of a source that corresponds to a wavelength of light that has been absorbed by electrons as the exited to higher energy levels
13
Q
Angle of refraction
A
The angle that refracted light makes with the normal of a boundary
14
Q
Annihilation
A
The process by which a particle and its antiparticle meet and their mass gets converted to energy in the form of a pair of gamma ray photons
15
Q
Anomalous result
A
A result that doesn’t fit in with the pattern of the other results in a set of data
16
Q
Antimatter
A
A name given to all anti particles
17
Q
Antineutrino
A
The antiparticle of a neutrino
18
Q
Antiparticle
A
A particle with the same rest mass and energy as its corresponding particle, but equal and opposite charge.
19
Q
Atom
A
A particle made up of protons and neutrons in a central nucleus, and electrons orbiting the nucleus
20
Q
Atomic number
A
The number of protons in an atom of an element
21
Q
Avogadro constant
A
The number of particles in a mole, defined as the number of atoms in exactly 12g of the carbon isotope c-12
22
Q
Background radiation
A
The weak level of nuclear radiation on earth from the surroundings
23
Q
Baryon
A
A type of hadron made up of three quarks. For example, protons and neutrons
24
Q
Baryon number
A
The number of baryons in a particle
25
Beta-minus decay
The type of decay in which an unstable nucleus of an atom emits a beta-minus particle (an electron) and anti neutrino
26
Beta-minus radiation
Nuclear radiation made up of electrons
27
Beta plus radiation
Nuclear radiation made up of positrons
28
Big bang theory
A theory to explain the formation of the universe. It says that the universe stared off very hot and very dense and that space has been expanding ever since
29
Binding energy
The energy releases when a nucleus forms, as well as the energy required to separate the nucleons in that nucleus. Equivalent to the mass defect
30
Black body
A body that absorbs all electromagnetic radiation of all wavelengths and emits them perfectly
31
Black hole
An object whose escape velocity is greater than the speed of light
32
Blue shift
The shift in wavelength and frequency of a source moving towards us from the blue end of the electromagnetic spectrum
33
Boltzmann’s constant, k
A constant used in the equation for the state of an ideal gas
34
Boyles law
For an ideal gas, at a constant temperature, the pressure p and volume v are inversely proportional
35
Breaking stress
The lowest stress that’s big enough to break a material
36
Brightness/ intensity
The power received from an object per unit area at Earth. Also known as intensity
37
Brittle
A material property which means the material doesn’t deform plastically, but snaps when the stress on it reaches a certain point
38
Capacitance
The amount of charge an object is able to store per unit potential difference across it
39
Capacitor
An electrical component that can store charge, made up of two conducting plates separated by a dielectric
40
Cathode
An electrode which becomes negatively charged
41
Centre of mass
The point at which you can consider all of an objects weight to act through
42
Centripetal acceleration
The acceleration of an object moving with circular motion. It’s directed towards the centre of the circle
43
Centripetal force
The force on an object moving with circular motion. It’s directed towards the centre of the circle, and is responsible for the objects curved path.
44
Charles’ law
For an ideal gas at constant pressure, the volume V is directly proportional to its absolute temperature T
45
Coherent (waves)
Sources that have the same wavelength and frequency and a fixed phase difference between them
46
Constructive interference
When two waves interfere to make a wave with a large displacement
47
Control rods
Rods inserted into a nuclear reactor to control the rate of fission by absorbing neutrons
48
Cosmological principle
On a large scale, the universe is homogenous and isotopic
49
Coulomb
A unit of charge, equal to the charge that passes in one second when current is one ampere
50
Couple
A pair of forced of equal size which act parallel to each other but in opposite decisions
51
Coupling medium
A liquid or gel used in ultrasound scans that displaces air and has an impedance close to that body of tissue
52
Critical angle
The angle of incidence at which the angle of refraction is 90 degrees
53
Critical damping
Damping such that the amplitude of oscillation is reduced in the shortest possible time
54
Current
The rate of flow of charge in a circuit, measured in amperes
55
Damping
A force which causes an oscillating object to lose energy and so causes the amplitude of the objects oscillation to decrease
56
Dark energy
A type of energy that fills the whole space, and might explain the accelerating expansion of the universe
57
De Broglie wavelength
The wavelength associated with a particle, as a part of theory of waveparticle duality
58
Decay constant
The probability of an atom decaying in unit time. A measure of how quickly an isotope will decay
59
Density
The mass per unit volume of a material or object
60
Destructive interference
When two waves interfere to make a wave with a reduced displacement
61
Diffraction
When waves spread out as they pass through a narrow gap or go round obstacles
62
Diffraction grating
A slide or other thin object that contains lots of equally spaced slits very close together
63
Diode
A component designed to allow current flow in one direction only
64
Displacement
How far an object has travelled from from its starting point in a given direction
65
Doppler effect
The change in the frequency and wavelength of a wave for a source moving towards or away from an observer
66
Drag
Friction caused by a fluid (gas or liquid)
67
Driving frequency
The frequency of a periodic external driving force which causes an object to oscillate
68
E.m.f
Electromotive force, the amount of electrical energy a power supply transfers to each coulomb of charge
69
Elastic collision
A collision that conserves both linear momentum and kinetic energy
70
Elastic limit
The force beyond which a material will be permanently stretched
71
Elastic strain energy
The energy stored in a stretched material
72
Electric field strength
The force per unit positive charge experienced by a body in an electric field
73
Electric potential
The electric potential energy that a unit positive charge would have at a specific point
74
Electric potential difference
The energy needed to move a unit charge between two points in an electric field
75
Electrocardiogram
A graph against time of the electrical signal measured at the surface of the body caused by the potential different between the polarised and depolarised parts of the heart
76
Electromagnetic force
A fundamental force that causes interactions between charged particles. Virtual photons are the exchange particle
77
Electromagnetic spectrum
A continuous spectrum of all the possible frequencies of electromagnetic radiation
78
Electron
A lepton with a relative charge of -1 and a relative mass of 0.0005 sometimes called a beta minus particle
79
Electron capture
The process of a proton rich nucleus capturing an electron to turn a proton into a neutron, emitting a neutrino
80
Electron degeneracy pressure
The pressure that stops electrons being forced into the atomic nucleus
81
Electron gun
A device that uses thermionic emission and a high potential difference to accelerate electrons
82
Electron volt
The kinetic energy carried by an electron after it has been accelerated through a potential difference of one volt
83
Endoscope
A long flexible tube containing a non-coherent bundle of optical fibres to carry light and a coherent bundle of optical fibres to transmit images
84
Equation of state for an ideal gas
The ideal gas equation applies to gas molecules rather than moles, pV=NkT
85
Equilibrium
When an object is at rest or moving with a constant velocity with no tendency to change
86
Escape velocity
The velocity that an object would need to travel at to have enough kinetic energy to escape a gravitational field
87
Excitation
The movement of an election to a higher energy level in an atom
88
Farad
The standard unit of capacitance. 1 farad = 1 coulomb per volt
89
Faradays law
The induced e.m.f is directly proportional to the rate of change of flux linkage
90
Flux linkage
The magnetic flux in a coil multiplied by the number of turns on the coil
91
Frequency
The. Umber of whole wave cycled per second passing a given point
92
Friction
A force that opposes motion. It arises when two objects are moving past each other
93
Fundamental frequency
The lowest resonant frequency produced by a standing wave
94
Fundamental particle
A particle which cannot be split up into smaller particles
95
Gamma radiation
Nuclear radiation made up of high-frequency electromagnetic waves/ photons
96
Geiger-Muller tube
An instrument used to detect nuclear radiation
97
Gravitational field strength
The force per unit mass, g, experienced by a body in a gravitational field
98
Gravitational force
A fundamental force which causes the attraction between objects with force proportional to their mass
99
Gravitational potential
The gravitational potential energy that a unit mass would have at a specific point
100
Gravitational potential energy
The energy stored in an object due to its position in a gravitational field
101
Hadron
A particle that is affected by the strong nuclear force
102
Half-life
The average time it takes for the number of unstable nuclei (of activity or count rate) in a sample of a radioactive isotope to halve
103
Halve-value thickness
The thickness of material required to reduce the intensity of x-rays to half its original value
104
Hertzsprung-Russel diagram
A graph of absolute magnitude against temperature or spectral class for stars
105
Hooke’s law
The extension of a stretched object is proportional to the load or force applied to it, up to the limit of proportionality
106
Hubble’s law
The recessional velocity of a distant object is proportional to its distance
107
Ideal has
A theoretical gas that obeys the three gas laws
108
Ideal gas equation
A combination of the three gas laws, given by pV=nRT
109
Impulse
The impulse acting in an object is equal to the change in momentum of the object
110
Inelastic collision
A collision that conserves linear momentum, but not kinetic energy
111
Intensity
The power received from an object per unit area at Earth. Also known as brightness
112
Intensity of sound
The amount of sound energy passing per second per unit area
113
Interference
The superposition of two or more waves
114
Internal resistance
The resistance created in a power source when electrons collide with atoms inside the power source and lose energy
115
Inverse square law
A law that relates two variables by a factors of 1/r^2
116
Isotope
Has the same proton number as the element but a different nucleon number
117
Isotropic
Meaning everything looks the same in every direction
118
Kinetic energy
The energy possessed by a moving object
119
Lenz’s law
The induced e.m.f is always in such a direction as to oppose the change that caused it
120
Lepton
A fundamental particle that is not affected by the strong nuclear force
121
Lepton number
The number of leptons in a particle, counted separately for different types of leptons
122
Light year
The distance that electromagnetic waves travel through a vacuum in one year
123
Light dependant resistor
A resistor with a resistance that spends on the intensity of light falling on it. The resistance decrease with increasing light intensity
124
Limit of proportionality
The point beyond which a force is no longer proportional to extension. Also known as the Hopkes law limit
125
Line absorption spectrum
A light spectrum with dark lines corresponding to different wavelengths of light that have been absorbed
126
Line emission spectrum
A spectrum of bright lines on a dark background corresponding to different wavelengths of light that have been emitted from a light source
127
Line spectrum
The pattern of lines produced by photons being emitted or absorbed by electrons moving between energy levels in an atom
128
Linear attenuation coefficient
A value for a material that shows how strongly X-rays are attenuated within a material
129
Longitudinal wave
A wave in which the vibrations are in the direction of travel of the wave
130
Lost volts
The energy wasted per coulomb overcoming the internal resistance of a power source
131
Luminosity
The total amount of energy emitted by an object in the form of electromagnetic radiation each second. Also known as power output
132
Magnetic field
A region in which a force acts in magnetic materials or magnetically susceptible materials
133
Magnetic flux
The magnetic flux (in Wb) passing through an area is given by the magnetic flux density multiplied by the area. It can also be thought of as the number of magnetic field lines passing through the area
134
Magnetic flux density
The value of magnetic flux density, in T, is given by the force in one metre of wire carrying a current of one amp at right angles to the magnetic field
135
Main sequence
A phase of a stars evolution in which the star is fusing hydrogen in its core
136
Mass
The amount of matter in an object
137
Mass attenuation coefficient
A measure of how much radiation is absorbed by a material per unit mass
138
Mass defect
The difference between the mass of nucleus, and the sum of the individual masses of the nucleons. Equivalent to the binding energy of the nucleus.
139
Mass number
The number of nucleons in an atom of an element
140
Matter
The name given to all particles
141
Mean square speed
The. Weave of the squared speeds of the particles in a gas
142
Internal energy
The sum of the potential and kinetic energy of an object
143
Meson
A type of hadron made up of a quark and an antiquark, for examples pions or kaons
144
Moderator (nuclear)
Material (often water) in a nuclear reactor that slows down neutrons so they can be captured by uranium nuclei, as well as absorbing them to reduce the chance of meltdown
145
Molar gas constant R
A constant used in the ideal gas equation equal to 8.31 j/mol/k
146
Molar mass
The mass that one mole of a substance would have
147
Mole
An amount of substance containing N particles, all of which are identical. N is the Avogadro constant
148
Moment
The turning effect of a force around a turning point
149
Momentum
The product of an objects mass and velocity
150
Monochromatic
A light source that is all the same wavelength or frequency
151
Natural frequency
The frequency of an object oscillating freely
152
Neutrino
A lepton with almost zero mass and zero charge
153
Neutron
A neutral baryon with a relative mass of 1
154
Neutron rich
Isotopes that contain many more neutrons than protons, making them unstable
155
Neutron star
A star made up of neutrons formed by the collapse of a red giant with a high core mass
156
Newton’s first law
The velocity of an object will remain constant unless a resultant force acts on it
157
Newtons second law
The rate of change of momentum of an object is proportional to the resultant force acting on it
158
Newton’s third law of motion
If an object A exerts a force on object B, then object B exerts an equal but opposite force on A
159
Nuclear fission
The spontaneous or induced splitting of a larger nucleus into two smaller nuclei
160
Nuclear fusion
The fusing of two smaller nuclei to form one larger nuclei
161
Nuclear radiation
Particles or energy released by an unstable atom as it decays
162
Nucleon
A particle that makes up an atomic nucleus (a proton or neutron)
163
Nucleon number
The total number of nucleons in an atomic nucleus
164
Nucleus
The small positive core of an atom where most of the atoms mass is concentrated, containing protons and neutrons
165
Ohmic conductor
A component that has a fixed resistance for a particular temperature
166
Ohms law
Provided the temperature is constant, the current through an ohmic conductor is directly proportional to the potential difference across it
167
Optical density
The property of a medium that describes how fast light travels through it.
168
Orbital period
The time taken for a satellite to complete a full orbit
169
Orbital speed
The speed at which a satellite travels
170
Overdamping
Heavy damping such that the system takes longer to return to equilibrium than a critically damped system
171
Pair production
A process of converting energy to mass in which a gamma ray photon has enough energy to produce a particle- antiparticle pair
172
Parallax
A measure of how much a nearby object (star) appears to move in relation to a fixed background due to the observers motion
173
Parsec
The distance of an object from earth if its parallax angle is equal to 1 arc second/ 1/3600 degrees
174
Path difference
The amount by which the path travelled by one wave is longer than the path travelled by another wave
175
Period
The time taken for a rotating or oscillating object to complete one cycle
176
Phase difference
A measure of how much one wave lags behind another wave. Measured in degrees or radians or fractions of a cycle
177
Photoelectric effect
The emission of electrons from a metal when light of a high enough frequency is shone on it
178
Photon
A discrete wave packet of electromagnetic radiation
179
Piezoelectric crystals
Crystals that produce difference when they are deformed or vice versa
180
Planetary nebula
The remnants of the outer layers of a red giant, that are ejected as the star becomes a white dwarf
181
Point charge
A charge with negligible volume, or a uniform sphere whose charge acts as if it is concentrated at the centre
182
Polarised wave
A wave in which all the vibrations are in one direction or plane
183
Polarising filter
A filter that only transmits vibrations if a wave in one direction or plane, called the plane of transmission
184
Positron
The antiparticle of an electron. Sometimes called a beta-plus particle
185
Potential difference
The work done in moving a unit charge between two points in a circuit
186
Potential divider
A circuit containing a voltage source and pair of resistors. The voltage across one of the resistors is used as an output voltage.
187
Potential energy
Energy that is stored
188
Power
The rate of transfer of energy or the rate of doing work
189
Power output
The total amount of energy emitted by an object in the form of electromagnetic radiation each second. Also known as luminosity
190
Pressure law
For an ideal gas at constant volume, the pressure p is directly proportional to its absolute temperature T
191
Principle of conservation of energy
Energy cannot be created or destroyed. Energy can be transferred from one form to another.
192
Progressive wave
A moving wave that carries energy from one place to another without transferring any material
193
Proton
A positively charged baryon with a relative mass of 1
194
Proton number
The number of protons in an atomic nucleus, Z.
195
Proton rich
Isotopes that have a high proton to neutron ratio are proton rich, making them unstable. They typically undergo beta-plus decay.
196
Quark
A fundamental particle that makes up hadrons
197
Radial field
A field symmetric about a central point
198
Radian
A unit of measurement for angles. There are 2 pi radians in a complete circle
199
Radioactive decay
When an unstable atom breaks down to become more stable, by releasing energy and or particles
200
Radioactive source
A material that emits alpha, beta or gamma radiation as it decays
201
Radiocarbon dating
A technique used to date objects by detecting the amount of active carbon 14 present.
202
Random error
An error introduced by variables which you can’t control
203
Recessional velocity
The speed at which an object is receding from earth
204
Red giant
Stars with a high luminosity and low temperature. A red giant is a phase of a stars evolution in which the star is fusing larger elements than hydrogen in its core or there is fusion in its shells. The fusion energy causes its outer layers to expand and cool, making it appear red.
205
Red shift
The shift in wavelength and frequency of a source moving away from us, towards or beyond the red end of the electromagnetic spectrum
206
Reflection
When a wave bounces back as it hits a boundary
207
Refraction
When a wave changes direction and speeds as it enters a medium with a different optical density
208
Refractive index
The ratio between the speed of light in a vacuum and the speed of light in a material
209
Resistance
A component has resistance of one ohm if a potential difference of one volt across it makes a current of one ampere flow through it.
210
Resistivity
The resistance of one metre length of a material with a one square metre cross sectional area. It’s measured in Ohm metres
211
Resonance
When an object, driven by a periodic external force at a frequency close to its natural frequency, begins to oscillate with a rapidly increasing amplitude
212
Resonant frequency
A frequency in which a stationary wave is formed because an exact number of waves are produced Ed in the time it takes for a wave to get to the end of the vibrating medium and back again
213
Root mean square speed
The square root of the average of the squared speeds of the particles in a gas
214
Satellite
A smaller mass that orbits a larger mass
215
Scalar
A quantity with a size but no direction
216
Swarzchild radius
The even horizon of a black hole
217
Second harmonic
A resonant frequency of a stationary wave which the wavelength is the length of the string
218
Semiconductor
A group of materials which conduct electricity. When their temperature rises, they can release more charge carriers
219
Simple harmonic motion
The oscillation of an object where the objects acceleration is directly proportional to its displacement from its equilibrium position, and is always directed towards the equilibrium.
220
Simple harmonic oscillators
A system that oscillates with simple harmonic motion
221
Specific heat capacity
The amount of energy needed to raise the temperature of 1kg of a substance by 1 k
222
Specific latent heat
The quantity of thermal energy required to change the state of 1kg of a substance
223
Speed
How fast something is moving, regardless of direction
224
Stationary wave
A wave with fixed positions of minimum and maximum oscillation created by the superposition of two progressive waves with the same frequency and amplitude moving in opposite directions
225
Stefans law
The power output of a black body is proportional to the south’s power of the body’s temperature and is directly proportional to its surface area
226
Step-down transformer
A transformer that decreases the voltage of an alternating current
227
Step-up transformer
A transformer that increase the voltage of an alternating current
228
Strain
The change in length divided by the original length of the material
229
Stress
The force applied divided by the cross sectional area
230
Strong nuclear force
A fundamental force with a short range which is repulsive at a very small separations and attractive at small separations. Responsible for the stability of nuclei
231
Supernova
The explosion of a high mass star after its red-giant phase, caused by the core collapsing and the outer layers of the star failing in and rebounding creating huge shockwaves
232
Superposition
The combination of displacements experienced in the instant that two wakes pass each other
233
Systematic error
An error introduced by the experimental apparatus or methodb
234
Tensile force
A force which stretches something
235
Tensile strain
The change in length divided by the original length of the material
236
Tensile stress
The force applied divides by the cross sectional area
237
Terminal velocity
The maximum velocity of an object through a fluid reached when the driving force is matched by the frictional force
238
Tesla
The Tesla is the unit of magnetic flux density L, equal to one Weber per square metre
239
Thermistor
A resistor with a resistance that depends on its temperature
240
Time constant
The time taken for the charge of a discharging capacitor to fall 73% or for the charge of a charging capacity to rise 63%
241
Total internal reflection
When all light is completely reflected back into a medium at a boundary with another medium, instead of some of it being refracted. It only happens at angles of incidence greater than the critical angle
242
Transformer
A device that makes use of electromagnetic induction to change the size of the voltage of an alternating current
243
Transverse wave
A wave in which the oscillations are at right angles to the direction of travel of the wave
244
Ultimate tensile stress
The maximum stress that a material can withstand
245
Ultrasound
Sound with a frequency higher than humans can hear (>20,000 Hz)
246
Velocity
The rate of change of displacement
247
Viscosity
A particle that only exists for a short amount of time
248
Volt
A unit of potential difference, equal to the amount of energy converted when a moving one coulomb of charge through a component
249
Watt
The unit of power, defined as a rate of change of energy transfer equal to one joule per second
250
Wave speed
The speed that a wave travels at
251
Wavelength
for length of one whole wave oscillation or wave cycle, e.g the distance between two crests of a wave
252
Wave particle duality
The idea that particles and waves can each display both particle and wave like behaviour
253
Weak interaction (weak nuclear force)
A fundamental force that has a short range and can change the character of a quark
254
Weber
The Weber is the unit of magnetic flux
255
Weight
The force experienced by mass due to a gravitational field
256
White dwarf
Stars with low luminosity and high temperature, left behind when a low mass star stops fusing elements and contracts
257
Weins displacement law
The higher the surface temperature of a black body, the shorter the peak wavelength of its radiation
258
Work function
The minimum amount of energy required for an election to escape a metals surface
259
X-ray tube
A device in which x-rays are produced by firing electrons at a rotating tungsten anode
260
Young’s modulus
The stress divided by strain for a material up to its limit of proportionality
261
262
