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.