Glossary Flashcards
Absolute magnitude
The magnitude a star would have if it were viewed from a distance of 10pc.
Absorption
Process of removing light or sound energy.
Absorption spectrum
Continuous spectrum crossed by dark lines or bands due to reduction of energy of particular frequencies when the light passes through a medium.
Acceleration
Change of velocity per unit time.
Amplitude
The maximum displacement of a vibrating particle.
Amplitude modulation
Process of transferring information by varying the amplitude of a wave.
Analogue
Continuously varying signal; its value is proportionally a physical quantity.
Annihilate
When a particle and its antiparticle meet, they destroy each other and become radiation.
Antinode
Fixed point in a stationary wave pattern where the amplitude is a maximum.
Antiparticle
There is an antiparticle for every particle. A particle and its corresponding antiparticle have equal rest mass and, if charged, equal and opposite charge.
Apparent magnitude
The magnitude of a star as it is observed from earth.
Asperity
Roughness of a surface.
Attack
The beginning of a musical sound when a note is played on an instrument.
Band spectrum
The coloured bands observed from molecules at high temperature; observed as a range of frequencies.
Bandwith
The range of frequencies in a transmitted signal.
Baryon number
Numbers assigned to quarks and hadrons that must be conserved in an interaction.
Baryons
A hadron consisting of three quarks.
Big Bang
Theory that all the energy of the universe originated from one point and that there universe began from expansion at that point.
Bit rate
Number of binary digits transmitted per second.
Black body
A body that emits all possible wavelengths for the temperature of that body.
Bosons
Particles, like photons, kaons and pions; gauge bosons carry the fundamental forces between particles.
Brightness
Observed intensity of a source.
Channel bandwidth
The range of frequencies allocated to a user.
Compressions
Regions of high pressure for a longitudinal wave.
Consonant
Two or more notes which when played together produce a pleasing sound.
Constructive interference
Interference in which two waves superpose to produce a wave with amplitude equal to the sum of the amplitudes of the two waves.
Continuous spectrum
Spectrum that contains no gas; all frequencies are present.
Critical angle
The angle of incidence that a light ray must exceed for total internal reflection to occur.
Critical temperature
Temperature at which a conduction of electricity becomes superconducting
Current
Rate of flow of charge.
Decay
Process occurring win radioactive particles emit radiation.
Decibel (dB)
Measure of sound intensity; an increase of 3dB is doubling of intensity.
Deep inelastic scattering
Scattering that occurs when a high energy particle collides with another particle producing new particles.
Demodulating
Process of retrieving information from a transmitted amplitude modulated or frequency modulated signal.
Destructive interference
Interference in which two waves superpose to produce a wave with amplitude equal to the difference in the amplitudes of the two waves.
Diffraction
Spreading of waves on passing a gap or near an edge.
Digital
Information sent in the form of binary digits.
Displacement
Distance from a reference point in a given direction.
Drag force
The force of fluid resistance on an object moving through the fluid.
Efficiency
The ratio of useful energy transferred (or useful work done) by the machine or device to energy supplied to it.
Elastic
A property that enables a solid to regain its shape after is has been deformed or distorted.
Elastic potential energy
Energy stored in a solid when it is extended or compressed by a force.
Electromagnetic wave
An electric and magnetic wave packet or photon that can travel through free space.
Electromotive force
The amount of electrical energy per unit charge produced by a source of electrical energy.
Electron energy level
Energies which electrons can have when bound to an atom.
Electron
Fundamental lepton that is a constituent of atoms.
Electroweak force
Term that describes the electromagnetic interaction and the weak interaction between particles.
Emission spectra
A spectrum that comes from a source without passing through an absorbing medium.
Equilibrium
Situation in which there is no resultant force acting on a body; the body remains at rest or travels at a constant velocity.
Error bar
Line representing the probable error on a graph.
Error of measurement
Uncertainty of a measurement.
Excitation
Process of electrons moving to a higher energy level.
Excited states
Electron states that are higher than the ground states.
Fourier synthesis/analysis
The process of determining which sinusoidal waves combine to produce a different periodic wave.
Free body
Diagram which shows the magnitude and direction of all forces acting upon an object.
Free fall
Situation when the only force acting on a falling body is gravitational.
Frequency
The number of cycles of a wave that pass a point per second, the number of of complete to and fro oscillations that occur per second.
Frequency modulation
Process of transferring information by varying the frequencies of a wave.
Fundamental particles
Particles that are not made from smaller particles.
Geostationary orbit
Orbit of a satellite that remains above the same point of the earths surface.
Graded index core
Glass fibre whose refractive index decreases from the centre to the edge.
Gravitational potential energy
Energy of an object due to its position relative to a particle or body that has mass.
Graviton
The particle that is thought to mediate the gravitational force.
Ground state
The lowest energy state that an electron can occupy in an atom.
Ground waves
Transmitted wave that travels along the surface of the earth.
Hadrons
Particles and antiparticles that can interact through the strong interaction.
Harmonic
Frequencies that are a multiple of the fundamental frequency of an oscillator. f, 2f, 3f etc.
Higgs boson
The particle that has been proposed as being responsible for the mass of particles.
Impulse
Force on a body x time for which the force acts = change in momentum of a body.
Inelastic
When a body undergoes an elastic process some energy that is supplied changes form so it is not recoverable in its initial form.
Infrasound
Sound that has a frequency below the lowest audible sound (about 16Hz)
Intensity
The energy per square metre that arrives on a surface each second.
Interference
Formation of points of cancellation and reinforcement where two coherent waves pass through each other.
Internal energy
The sum of the potential and kinetic energies of all the atoms in a body.
Internal resistance
Resistance inside a source of electrical energy, the loss of pd per unit current in the source when current passes through it.
Ion
Charged atom.
Ionisation
Process of creating ions.
Ionisation energy
Energy that has to be supplied to an atom to remove an electron.
Ionising radiation
Radiation that is able to provide energy to ionise atoms.
Isotopes
Atoms of an element with different numbers of neutrons and the same number of protons.
Kinetic energy
Energy due to the motion of a body.
Leptons
Collective term for fundamental particles.
Line spectrum
Spectrum produced by diffraction gratings using radiation produced by excitation and relaxation of electrons in atoms.
Longitudinal wave
Waves with a direction parallel to the direction of travel of the waves.
Loudness
Subjective perception of the intensity of a sound.
Luminosity
The property of a source that gives the perception of brightness of a source.
Mesons
A hadron consisting go a quark and an antiquark.
Modes
A possible frequency of vibration.
Modulating
The process of changing the amplitude or frequency of oscillation of a wave.
Moments
Force x perpendicular distance from the line of action of the force to the point.
Momentum
Mass x velocity
Multi path dispersion
The lengthening of a light pulse as it travels along an optical fibre due to rays that repeatedly undergo total internal reflection having to travel a longer distance than rays that undergo less total internal reflection.
Musical interval
An interval between two notes on a musical scale determined by the ratio of frequencies of the notes.
Natural frequency
The oscillation that takes place when an oscillating system is displaced from its original position and allowed to vibrate freely.
Node
Fixed point on a stationary wave pattern where the amplitude is zero.
Nucleon number
The number of neutrons and protons in a nucleus; also referred to as mass number.
Nucleon
Neutron or proton in the nucleus.
Nuclide
A nucleus with a particular number of protons and neutrons.
Octave
Musical interval between harmonics that have frequency f and 2f.
Ohm’s law
The pd across a metallic conductor is proportional to the current provided by the physical conditions do not change.
Oscilloscope
Instrument that produces an image of the variation with time of p.d.
Pair production
When a gamma photon changes into a particle and antiparticle.
Path difference
The difference in distances from two coherent sources to an interference fringe.
Perfect pitch
The ability to identify the musical pitch of a note exactly.
Period
Time for one complete cycle of a wave to pass a point; time for one complete oscillation.
Phase difference
The fraction of a cycle between the vibrations of two vibrating particles, measured either in radians or degrees.
Photoelectric effect
Emission of electrons from a metal surface when the surface is illuminated by a frequency greater than a minimum value known as threshold frequency.
Photon
Packet or ‘quantum’ of electromagnetic waves.
Pitch
Subjective quality relating to the position of a note on a musical scale determined by its frequency.
Polarised
Transverse waves that vibrate in one plane only.
Positron
Antiparticle of the electron.
Potential difference
Work done or energy transfer per unit charge between two points when charge moves from one point to the other.
Power
Rate of transfer of energy.
Precision of an instrument
The smallest non zero reading that can be measured.
Projectile
An unpowered object thrown or fired through the air.
Pulse code modulation
Modulation in which a signal is sampled and only certain discrete values of the information are transmitted binary coded signal.
Quality
The property that enables instruments of the same pitch to be recognised: determined by the frequencies present in the sound.
Quantised
Only certain discrete values of a physical quantity are possible.
Quarks
Fundamental particles that combine to form hadrons (baryons and mesons).
Radiation
Energy transmitted as em waves or particles (alpha and beta).
Random error
Error of measurement due to readings that vary randomly with no recognisable pattern.
Range of set of a readings
The range of set of a readings of the same measurement is the difference between the minimum and maximum reading.
Range of an instrument
The difference between the minimum and the maximum reading that can be obtained using an instrument.
Rarefactions
Regions of low pressure for a longitudinal wave.
Rays
Paths taken by energy, e.g light
Recessional speed
Speed at which galaxies are moving away from the Earth.
Red shift
The movement of waves to longer wavelengths than those observed from a similar source in a laboratory on earth.
Reflection
Process in which a wave or particle is directed back into the medium from which it came when it is incident on a surface.
Relaxation
The process in which an excited returns to a lower energy state by emitting a photon.
Repeaters
Used to boost the energy of a signal during transmission.
Resistance
Pd / current .
Resistivity
Resistance per unit length x area of cross section.
Resonating
A condition when the body is begin driven by a frequency that is equal to its natural frequency leading to a maximum amplitude of vibration.
Resultant
Combined effect of a number of vector quantities (e.g force or velocity).
Sampling
A process of taking the value of a physical quantity at regular intervals for transmission or processing.
Scalars
A physical quantity of a magnitude only.
Sky waves
Transmitted radio waves that are received back on earth after being deflected by the ionosphere.
Space waves
Short wavelength radio waves that penetrate the ionosphere and can only be used for line of sight communication with the earth.
Standing wave
Wave pattern with nodes antinodes formed when two or more progressive waves of the same frequency and amplitude pass through each other.
Strangeness
A strangeness number is assigned to every particles and antiparticle on the basis that strangeness in always conserved in the strong interaction by not the weak interaction or decay involving a quark or antiquark.
Strong force
Attractive force between nucleons that holds them in the nucleus.
Superposition
The effect of two waves adding together when they meet.
Third
Interval between the first and third note of a major musical scale.
Threshold frequency
Minimum frequency of light that can cause photoelectric effect.
Threshold of hearing
Lowest intensity of sound that is audible.
Timbre
The property that enables instruments of the same pitch to be recognised: determined by the frequencies present in the sound.
Torque
Force x perpendicular distance from the line of action of the force to the point.
Total internal reflection
A light ray travelling in a substance is totally internally reflected at a boundary with a substance of lower refractive index if the angle of induce is greater than a certain value known as critical angle.
Transverse wave
Waves with a direction of vibration perpendicular to the direction of propagation of the wave’s energy.
Travelling waves
Waves for which the position of maximum displacement moves so that the wave is propagated.
Tremolo
A note played by a continually changing that amplitude of the note or a continuous rapid change between two notes.
Ultrasound
Sound that has a higher frequency than the highest audible sound (20,000 Hz).
Ultraviolet catastrophe
The failure of classical physics to explain the nature of radiation from a black body.
Unbalanced force
A force for which there is not an equal and opposite force acting on a particular object.
Vector
A physical quantity with magnitude and direction.
Velcocity
Change of displacement per unit time.
Vibrato
A note played with a slight quick continually varying pitch.
Viscosity
Property of a fluid (liquid or gas) to oppose the motion within it.
Wavefronts
A surface or line along which all oscillations for a given frequency are in phase (wavefronts are perpendicular to rays).
Wavelength
Distance qual to the least distance between two successive crests or compressions.
Wave-particle duality
Matter particles have a wave like nature as well as a particle like nature, photons have a particle like nature as well as wave like nature.
Work
Force x distance moved in the direction of the force.
Work function
Minimum amount of energy needed by an electron to escape a metal surface.
