AS Definitions Flashcards
(217 cards)
1
Q
Absolute refractive index
A
The ratio between the speed of light in a vacuum and the speed of light in a material
2
Q
Absolute uncertainty
A
The uncertainty of a measurement given as a fixed quantity
3
Q
Absorption (fibre optics)
A
Where some of the energy of a fibre-optic signal is absorbed by the material of the optical fibre
4
Q
Acceleration
A
The rate of change of velocity
5
Q
Accurate result
A
An accurate result is really close to the true answer
6
Q
Alpha decay
A
A type of decay in which an unstable nucleus of an atom emits and alpha particle
7
Q
Alpha particle
A
A particle made up of two protons and two neutrons
8
Q
Ammeter
A
A component used to measure the current flowing through a circuit
9
Q
Amplitude
A
The maximum displacement of a wave, i.e. The distance from the undisputed position to a crest or trough
10
Q
Angle of incidence
A
The angle that incoming light makes with the normal of a boundary
11
Q
Angle of refraction
A
The angle that refracted light makes with the normal boundary
12
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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
13
Q
Anomalous result
A
A result that doesn’t fit in with the pattern of the other results in a set of data
14
Q
Antimatter
A
The name given to all antiparticles
15
Q
Antineutrino
A
The antiparticle of a neutrino
16
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Antineutron
A
The antiparticle of a neutron
17
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Antinode
A
A point of maximum amplitude in a stationary wave
18
Q
Antiparticle
A
A particle with the same rest mass and energy as its corresponding particle, but equal and opposite
19
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Antiproton
A
The antiparticle of a proton
20
Q
Atom
A
A particle made up of protons and neutrons in a central nucleus, and electrons orbiting the nucleus
21
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Atomic number
A
The number of protons in an atom of an element
22
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Average velocity
A
The change in displacement of an object divided by the time taken
23
Q
Baryon
A
A type of hadron made up of three quarks. For example, protons and neutrons
24
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Baryon number
A
The number of baryons in a particle
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Beta minus decay
A trop of decay in which an unstable nucleus of an atom emits a beta minus particle (an electron) and an antineutrino
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Beta plus decay
A type of decay in which an unstable nucleus of an atom emits a beta plus particle (a positron) and a neutrino
27
Breaking stress
The lowest stress that's big enough to break a material
28
Brittle
A brittle material doesn't deform plastically, but snaps when the stress on it reaches a certain point
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Brittle fracture
When a stress applied to a brittle material causes tiny cracks at the material's surface to get bigger until the material breaks completely
30
Calibration
Making a scale on a measuring instrument or checking a scale by measuring a known value
31
Categoric data
Data that can be sorted into categories
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Centre of mass
The point which you can consider all of an object's weight to act through
33
Circuit symbol
A pictorial representation of an electrical component
34
Cloud chamber
A chamber filled with a vapour which is used to track the motion of charged particles
35
Coherent
Sources (or waves) that have the same wavelength and frequency and a fixed phase difference between them are coherent
36
Compressive force
A force which squashes something
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Conservation of energy (principle of)
Energy cannot be created or destroyed. It can be transferred from one form to another, but the total amount of energy in a closed system will not change
38
Constructive interference
When two waves interfere to make a wave with a larger displacement
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Continuous data
Data that can have any value on a scale
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Control variable
A variable that is kept constant in an experiment
41
Cosmic ray showers
Lots of high-energy particles that are produced from cosmic rays interacting with molecules in the atmosphere
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Cosmic rays
Radiation in the form of charged particles that come from space and hit the Earth
43
Coulomb (C)
A unit of charge. One coulomb is the amount of charge that passes in 1 second when the current is 1 ampere
44
Couple
A pair of forces of equal size which act parallel to each other but in opposite directions
45
Critical angle
The angle of incidence at which the angle of refraction is 90 degrees
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Crumple zone
Part of a car or other vehicle designed to deform plastically in a crash so less energy is transferred to the people inside
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Current
The rate of flow of charge in a circuit. Measured in amperes (A)
48
Density
The mass per unit volume of a material or object
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Dependent variable
The variable that you measure in an experiment
50
Destructive interference
When two waves interfere to make a wave with a reduced displacement
51
Diffraction
When waves spread out as they pass through a narrow gap or go round obstacles
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Diffraction grating
A slide or other thin object that contains lots of equally spaced slots very close together, used to show diffraction patterns of waves
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Diode
A component designed to allow current flow in one direction only
54
Discrete data
Data that can only take certain values
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Dispersion
A form of signal degradation that causes pulse broadening of a fibre optic signal as it travels
56
Displacement
How far an object has travelled from its starting point in a given direction. In the case of a wave, it is the distance a point on wave has moved from its undisturbed position
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Drag
Friction caused by a fluid
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Efficiency
The ratio between useful energy given out by a machine to the amount of energy put into the machine
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Elastic
An elastic material returns to its original shape/ length once the forces acting on it are removed
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Elastic limit
The force (or stress) beyond which a material will be permanently stretched
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Elastic strain energy
The energy stored in a stretched material
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Electromagnetic force
A fundamental force that causes interactions between charged particles. Virtual photons are the exchange particle
63
Electromagnetic spectrum
A continuous spectrum of all the possible frequencies of EM radiation
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Electromotive force (emf)
The amount of electrical energy a power supply transfers to each coulomb of charge
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Electron
A lepton with a relative charge of -1 and a relative mass of 0.0005. Sometimes called a β- particle
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Electron capture
The process of a proton-rich nucleus capturing an electron to turn a proton into a neutron, emitting a neutrino
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Electron-proton collision
The process of an electron colliding with a proton and producing a neutron and a neutrino
68
Electron volt
The kinetic energy carried by an electron after it has been accelerated from rest through a potential difference of one volt
69
Equilibrium
An object is in equilibrium if all the forces acting on it cancel each other out
70
Evidence
Valid data arising from an experiment, which can be used to support a conclusion
71
Exchange particle
A virtual particle which allows force to act in a particle interaction. They are also known as gauge bosons
72
Excitation
The movement of an electron to a higher energy level in an atom
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Fair test
An experiment in which all variables are kept constant apart from the independent and dependent variables
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First harmonic
The lowest frequency at which a stationary wave is formed where the wavelength is double the length of the vibrating medium
75
Fractional uncertainty
The uncertainty given as a fraction of the measurement taken
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Free fall
The motion of an object undergoing an acceleration of g
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Frequency
The number of whole wave cycles (oscillations) per second passing a given point. Or the number of whole wave cycles given out from a source per second
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Friction
A force that opposes motion. It acts in the opposite direction to the motion. It arises when two objects are moving past each other, or an object is moving through a fluid
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Fundamental particle
A particle which cannot be split up into smaller particles
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Gauge boson
A virtual particle which allows forces to act in a particle interaction. They are also known as exchange particles
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Geiger counter
A device to measure the amount of ionising radiation
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Gravitational force
A fundamental force which causes attraction between objects with a force proportional to their masses
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Gravitational potential energy
The energy an object gains when lifted up in a gravitational field, due to its position
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Ground state
The lowest energy level of an atom or the lowest energy level for an electron in an atom
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Hadron
A particle made up of quarks that is affected by the strong nuclear force
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Hooke's law
The extension of a stretched object is proportional to the load or force applied to it. This applies up to the limit of proportionality
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Hooke's law limit
The point beyond which force is no longer proportional to extension. Also known as the limit of proportionality
88
Hypothesis
A suggested explanation for a fact or observation
89
I-V characteristic
A graph which shows how the current flowing through a component changes as the potential difference across it is increased
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Impulse
The impulse acting on an object is equal to the change in momentum of the object
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Independent variable
The variable that you change in an experiment
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Instantaneous velocity
The velocity of an object at a particular moment in time
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Intensity (of light)
The power per unit area
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Interference
The superposition of two or more waves
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Internal resistance
The resistance created in a power source when electrons collide with atoms inside the power source and lose energy
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Ionisation
The process where an electron is removed from (or added to) an atom
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Ionisation energy
The energy required to remove an electron from an atom in its ground state
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Isotope
One of two or more forms of an element with the same proton number but a different nucleon number
99
Isotopic data
The relative amounts of isotopes in a substance
100
Kinetic energy
The energy possessed by a moving object due to its movement
101
Lepton
A fundamental particle that is not affected by the strong nuclear force
102
Lepton number
The number of leptons in a particle. Lepton number is counted separately for different types of leptons
103
Lever
A structure made of a rigid object rotating around a pivot, in which an effort force works against a load force
104
Lift
An upwards force on an object moving through a fluid
105
Light-dependent resistor (LDR)
A resistor with a resistance that depends on the intensity of light falling on it. The resistance decreases with increasing light intensity
106
Line absorption spectrum
A light spectrum with dark lines corresponding to different wavelengths of light that have been absorbed
107
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
108
Line spectrum
A pattern of lines produced by photons being emitted or absorbed by electrons moving between energy levels in an atom
109
Longitudinal wave
A wave in which the oscillations are parallel to the direction of energy propagation
110
Lost volts
The energy wasted per coulomb overcoming the internal resistance of a power source
111
Mass
The amount of matter in an object
112
Mass number
The number of nucleons in an atom of an element
113
Material dispersion
Dispersion caused by different wavelengths of light traveling at different speeds through the material of an optical fibre
114
Matter
The name given to all particles
115
Maximum (interference)
A point in an interference pattern where the intensity is locally brightest (a location of constructive interference)
116
Meson
A type of hadron made up of a quark and an antiquark. For example, pions or kaons
117
Minimum (interference)
A point in an interference pattern where the intensity is locally lowest (a point of destructive interference)
118
Modal dispersion
Dispersion caused by reflected light taking paths of different lengths in an optical fibre
119
Moment
The turning effect of a force around a turning point
120
Moment of a couple
The moment caused by two equal forces acting parallel to each other but in opposite directions around a turning point
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Momentum
The momentum of an object is the product of its mass and velocity
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Monochromatic
A light source that is all of the same wavelength (or frequency)
123
Neutrino
A lepton with (almost) zero mass and zero charge
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Neutron
A neutral baryon with a relative mass of 1
125
Newton's first law of motion
The velocity of an object will not change unless a resultant force acts on it
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Newton's second law of motion
The acceleration of an object is proportional to the resultant force acting on it
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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 object A
128
Node
A point of minimum amplitude on a stationary wave
129
Nuclear decay
The process of an unstable nucleus emitting particles in order to become more stable
130
Nucleon
A particle in the nucleus of an atom (which can be a proton or a neutron)
131
Nucleon number
The number of neutrons and protons in an atom of an element
132
Nucleus
The centre of an atom, containing nucleons
133
Nuclide notation
A notation that tells you the nucleon number, A, and proton number, Z, of an element
134
Optical density
The property of a medium that describes how fast light travels through it. Light moves slower through a medium with a higher optical density
135
Optical fibre
A thin flexible tube of glass or plastic that can carry light signals using total internal reflection
136
Ordered/ ordinal data
Categoric data where the categories can be put in order
137
Pair production
A process of converting energy to mass in which a gamma ray photon has enough energy to produce a particle-antiparticle pair
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Path difference
The amount by which the path travelled by one wave is longer than the path travelled by another wave
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Period
The time taken for one whole wave cycle to pass a given point
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Phase
A measurement of the position of a certain point on a wave cycle, measured as an angle (in degrees or radians) or in fractions of a cycle
141
Phase difference
The amount by which one wave lags behind another, measured as an angle (in degrees or radians) or in fractions of a cycle
142
Photoelectric effect
The emission of electrons from a metal when light of a high enough frequency is shone on it
143
Photoelectron
An electron released through the photoelectric effect
144
Photon
A discrete wave-packet of EM waves
145
Plastic
A plastic material is permanently stretched once the forces acting on it are removed
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Polarised wave
A wave in which all the vibrations are in one direction or plane
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Polarising filter
A filter that only transmits vibrations of a wave in one direction or plane, called the plane of transmission
148
Potential difference
The work done moving a unit charge between two points in a circuit
149
Potential divider
A circuit containing a voltage source and a pair of resistors. The voltage across one of the resistors is used as an output voltage. If the resistors aren't fixed, the circuit will be capable of producing a variable output voltage
150
Power
The rate of transfer of energy or the rate of doing work. It's measured in watts (W), where 1 watt is equivalent to 1 joule per second
151
Precise result
The smaller the amount of spread of your data from the mean, the more precise it is
152
Principle of conservation of energy
Energy cannot be created or destroyed. Energy can be transferred from one form to another but the total amount of energy in a closed system will not change
153
Progressive wave
A moving wave that carries energy from one place to another without transferring any material
154
Projectile motion
Motion with a constant horizontal velocity and a vertical velocity affected by acceleration due to gravity
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Proton
A positively charged baryon with a relative mass of 1
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Pulse broadening
When signal in an optical fibre gets wider as it is transmitted, due to dispersion
157
Quantum number
A number hat represents a property of a particle that must be conserved in all interactions; for example, baryon number and lepton number. (Strangeness is an exception to this as it is not conserved in weak interactions)
158
Quark
A fundamental particle that makes up hadrons
159
Random error
An error introduced by variables which you cannot control
160
Reflection
When a wave bounces back as it hits a boundary
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Refraction
When a wave changes direction and speed as it enters a medium with a different optical density
162
Relative refractive index
The ratio of the speed of light in one material to the speed of light in a second material
163
Resistance
A component has a resistance of 1Ω if a pd of 1V across it makes a current of 1A flow through it.
164
Resistivity
The resistance of a 1m length of a material with a 1m2 cross-sectional area. It is measured in ohm-metres
165
Repeatable result
A result is repeatable if you can repeat an experiment multiple times and get the same results
166
Reproducible result
A result is reproducible if someone else can recreate your experiment using different equipment or methods, and get the same result you do
167
Resolution
The smallest change in what's being measured that can be detected by the equipment
168
Resonant frequency
A frequency at which a stationary wave is formed because an exact number of waves are produced in the time it takes for a wave to get to the end of the vibrating medium and back again
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Rest energy
The amount of energy that would be produced if all of a particle's mass were transformed into energy
170
Resultant vector
The vector that's formed when two or more vectors are added together
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Scalar
A quantity with a size but no direction
172
Second harmonic
A resonant frequency at which the wavelength is the length of the vibrating medium. It is twice the frequency of the first harmonic
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Semiconductor
A group of materials which conduct electricity (but not as well as metals). When their temperature rises, they can release more charge carriers and their resistance decreases
174
Signal degradation
When an optical signal loses amplitude or is broadened whilst travelling. This can lead to information loss
175
Spark counter
A device to detect ionising radiation
176
Specific charge
The charge per unit mass of a particle
177
Speed
How fast something is moving, regardless of direction
178
Stationary wave
A wave created by the superposition of two progressive waves with the same frequency (or λ) and amplitude, moving in opposite directions
179
Stiffness constant
The force needed to extend an object per unit extension. The units are Nm-1. Each object has its own stiffness constant
180
Stopping potential
The potential difference needed to stop the fastest moving photoelectrons in the photoelectric effect
181
Strain
The change in length divided by the original length of the material
182
Strangeness
A property which particles that contain strange quarks have. Strange particles are always produced in pairs
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Stress
The force applied divided by the cross-sectional area
184
Strong nuclear force
A fundamental force with a short range which is attractive at small separations and repulsive at very small separations. Responsible for the stability of nuclei
185
Superconductor
A material that has zero resistivity when cooled below a critical (transitional) temperature
186
Superposition
The combination of displacements experienced in the instant that two waves pass each other
187
Systematic error
An error introduced by the experimental apparatus or method
188
Tensile force
A force which stretches something
189
Tensile strain
The change in length divided by the original length of the material
190
Tensile stress
The force applied divided by the cross-sectional area
191
Terminal pd
The potential difference between the two terminals of a power supply. This is equal to emf when there is no internal resistance
192
Terminal speed
The speed at which the driving force(S) match the frictional force(S)
193
Thermistor (NTC)
A resistor with a resistance that depends on its temperature - it is a type of semiconductor
194
Threshold frequency
The lowest frequency of light that when shone on a metal will cause electrons to be released from it (by the photoelectric effect)
195
Total destructive interference
Destructive interference in which the waves completely cancel each other out
196
Total internal reflection
When all light is completely reflected back into a medium at a boundary with another medium, instead of being refracted. It only happens at angles of incidence greater than the critical angle
197
Transitional temperature
The critical temperature at and below which a superconductor has zero resistivity
198
Transverse wave
A wave in which the oscillations is perpendicular to the direction of energy transfer
199
Ultimate tensile stress (UTS)
The maximum stress that a material can withstand
200
Uncertainty
An interval in which the true value of a measurement is likely to lie, given with a level of confidence or probability that the true value lies in that interval
201
Vector
A quantity with a size and a direction
202
Velocity
The rate of change of displacement
203
Vibration transducer
A piece of equipment which has a moving plate that is able to oscillate rapidly at a set frequency
204
Virtual particle
A particle that only exists for a short amount of time, e.g. An exchange particle
205
Volt (V)
The unit of potential difference. The pd across a component is 1 volt when you convert 1 joule of energy moving 1 coulomb of charge through the component
206
Watt (W)
The unit of power. A watt is defined as a rate of energy transfer equal to 1 joule per second
207
Wave-particle duality
All particles have both particle and wave properties. Waves can also show particle properties
208
Wavelength
The length of one whole wave oscillation or wave cycle, e.g. The distance between two crests (or troughs) of a wave
209
Weak interaction
A fundamental force that has a short range and can change the character of a quark
210
Weight
The force experienced by a mass due to a gravitational field
211
Work
Work is the amount of energy transferred from one form to another when a force moves an object through a distance
212
Work function
The minimum amount of energy required for an electron to escape a metal's surface
213
Worst lines
Lines of best fit which have the maximum and minimum possible slopes for the data and which should go all of the error bars
214
Yield point (or yield stress)
The stress at which a large amount of plastic deformation takes place with a constant or reduced load
215
Young modulus
The stress divided by strain for a material, up to its limit of proportionality
216
Zero error
When a measuring instrument falsely reads a non-zero value when the true value being measured is zero
217
Zero order line
The line of maximum brightness at the centre of a diffraction grating interference pattern. It's in the same direction as the incident beam
