A set of cards for revision for unit 2 module exam
Terms : Hide Images
| 590255424 | mechanical wave | a wave that needs a medium to pass through | |
| 590255425 | medium | a material substance through which waves travel | |
| 590255426 | electromagnetic waves | a combination of a transverse electric and a transverse magnetic wave moving through space | |
| 590255427 | transverse wave | A wave in which the vibration is at right angles to the direction in which the wave is traveling. | |
| 590255428 | longitudinal wave | A wave in which the vibration is in the same direction as that in which the wave is traveling | |
| 590255429 | direction of propagation | direction of travel of a progressive wave | |
| 590255430 | progressive wave | a wave that travels | |
| 590255431 | compression | a part of a longitudinal wave where the particles are crowded together | |
| 590255432 | rarefaction | a part in a longitudinal wave where the particles are spread apart | |
| 590255433 | circular waves | waves where wavefronts progress outwards in concentric circles | |
| 590255434 | plane wave | waves where wavefronts progress outwards in parallel lines | |
| 590255435 | continuous waves | imaginary waves which have not beginning or end in a scientific model | |
| 590255436 | wavetrains | waves with a beginning and an end | |
| 590255437 | pulse | a short wave where no motion is repeated ( a single wave) | |
| 590255438 | wavefront | the observed(or imagined) line formed by the peak or trough of a transverse wave or compressions or rarefactions of a longitudinal wave which are one wavelength apart | |
| 590255439 | rays | imaginary lines at 90 degrees to wavefronts in the direction(s) of propagation | |
| 590255440 | wavespeed | = frequency x wavelength | |
| 590255441 | wavelength | is the distance from one point on a wave, to the very same point on the next wave. | |
| 590255442 | frequency | the number of waves per second | |
| 590255443 | Hertz | Unit of frequency - equivalent to 1/s | |
| 590255444 | period | time for one complete oscillation = 1/f | |
| 590255445 | amplitude | maximum displacement of any point on a transverse wave OR the maximum displacement of any point on a longitudinal wave from the equilibrium position | |
| 590255446 | quality | description of sounds (hollow, dull, crackle) | |
| 590255447 | timbre | The difference in sound when two tones have the same loudness, pitch, and duration. | |
| 590255448 | phase | points are in phase if they are at the same part of the cycle in that wave; waves are in phase if they begin at the same part of the wave and have the same frequency | |
| 590255449 | antiphase | a phase difference of half a wavelenth, 90 degrees or pi radians | |
| 590255450 | phase difference | the fraction of a wave by which two points on one wave or 2 waves differ in phase | |
| 590255451 | displacement | the size of the vibration of a wave | |
| 590255452 | principle of superposition | where 2 or more waves meet the total displacement at any point is the sum of the displacements that each individual wave would cause at that point | |
| 590255453 | path difference | the difference in distance travelled from source to destination by 2 waves | |
| 590255454 | stationary or standing waves | not a progressive wave, it has fixed positions of peaks and troughs | |
| 590255455 | node | region of zero displacement in a standing wave | |
| 590255456 | antinode | region of maximum displacement in a standing wave | |
| 590255457 | principle of superposition | the displacement of any point due to the superposition of wave systems is equal to the sum of the displacements of the individual waves at that point | |
| 590255458 | path difference | the difference in distance travelled from source to destination by 2 waves | |
| 590255459 | stationary or standing waves | not a progressive wave, it has fixed positions of peaks and troughs | |
| 590255460 | nodes | regions of zero displacement in standing wave | |
| 590255461 | antinodes | The positions on a standing wave where the largest amplitudes occur. | |
| 590255462 | fundamental frequency | the lowest frequency of vibration of a standing wave. In a string wavelength = 2 x length of string | |
| 590255463 | harmonics | possible frequencies of a standing wave given by: wavelength = (2 x length of string)/n where n is an integer > 0 | |
| 590255464 | resonance | when forced vibrations of a system such as a string or column of air result in a harmonic wave | |
| 590255465 | phase change | the change of phase of 180degrees or half a wavelength which occurs on reflection of a wave at a more dense medium | |
| 590255466 | law of reflection | angle of incidence = angle of reflection | |
| 590255467 | normal | imaginary line at 90 degrees to a boundary between different media | |
| 590255468 | Huygen's construction | Each point on a wavefront is a source of circular waves | |
| 590255469 | refraction | The change of direction of a wavefront between two substances in which the speed of the wave differs | |
| 590255470 | Snell's law | refractive index = sini/sinr = speed in medium 1/speed in medium 2 when a wave travels from medium 1 to medium 2 - i is angle of incidence, r is angle of refraction | |
| 590255471 | total internal reflection | occurs when light traveling from a region of a higher index of refraction to a region of a lower refraction strikes the boundary at an angle greater than the critical angle such that all light reflects back into the region of the higher index of refraction. | |
| 590255472 | critical angle | the angle of incidence that produces an angle of refraction of 90 degrees, at higher angles of incidence total internal reflection occurs | |
| 590255473 | transmitted | passes through substances | |
| 590255474 | diffraction | A change in the direction of a wave when the wave finds an obstace or an edge such as an opening. | |
| 590255475 | interference | when waves overlap to produce a pattern according to the principle of superposition | |
| 590255476 | de Broglie wavelength | the apparent wavelenth of a stream of particles which demostrate wave-particle duality | |
| 590255477 | fringes | series of light (from constructive interference) and dark (destructive interference) bands produced by illuminating multiple slits | |
| 590255478 | coherent | wave sources with a constant phase difference | |
| 590255479 | incoherent | wave sources witha changing phase difference, they cannot produce an interference pattern | |
| 590255480 | plane polarised | the phenomenon in which waves of electromagnetic radiation or other transverse waves are restricted to one plane of vibration | |
| 590255481 | unpolarised | a wave with oscillations occuring in many planes | |
| 590255482 | electromagnetic spectrum | family of waves predicted by James Clerk Maxwell which travel through a vacuum at the speed of light, obey wave speed equation, are transverse, are formed by oscillating electric and magnetic fields | |
| 590255483 | ionosphere | radio waves in the range 3-300MHz are reflected and refracted by this layer | |
| 590255484 | microwaves | radio waves which need a short aerial and are not reflected by the ionosphere | |
| 590255485 | infrared | responsible for heat radiation | |
| 590255486 | visible light | radiation in range 400-700nm | |
| 590255487 | ultraviolet | this radiation is used to kill bacteria and viruses in wastewater | |
| 590255488 | x-rays | absorbed by dense materials to show the hidden structures | |
| 590255489 | gamma rays | used to kill cancerous cells | |
| 590255490 | red shift | property of spectra emitted by stars in receding galaxies | |
| 590255491 | Doppler effect | observed increase in pitch of sound emitted by approaching objects and fall in pitch of receding objects | |
| 590255492 | Hubble's law | velocity of receding galaxy = Hubble's constant x distance to galaxy | |
| 590255493 | pulse echo | method of distance measurement using the observed time for a pulse to return | |
| 590255494 | Doppler radar | technique which combines doppler effect and pulse echo to determine the distance and speed of moving objects | |
| 590255495 | ultrasound | Sound above 20kHz used for medical diagnosis | |
| 590255496 | secondary source | not a source of energy in its own right | |
| 590255497 | primary source | oil, coal or gas | |
| 590255498 | electric current | rate of charge passing a given point | |
| 590255499 | coulomb (C) | unit of charge | |
| 590255500 | ampere (A) | unit of current | |
| 590255501 | conventional current | the flow of electric current described as the direction positive charge would flow | |
| 590255502 | charge | area under current-time graph | |
| 590255503 | electromotive force | energy supplied to each unit of charge from a cell (symbol E, units V) | |
| 590255504 | potential difference | energy transferred per unit charge to a component in a circuit which causes current to flow | |
| 590255505 | resistance | potential difference/current for a component in a circuit | |
| 590255506 | Ohm's Law | The current through a wire is proportional to the potential difference across its ends if other physical factors remain constant | |
| 590255507 | ohmic conductors | metal at constant temperature | |
| 590255508 | non-ohmic conductor | lamp filament or semiconductor diode | |
| 590255509 | resistivity | (resistance x cross sectional area) / length | |
| 590255510 | superconductor | a material with no resistivity - a perfect conductor | |
| 590255511 | transport equation | I= (NAle)/t for electrons, I=nAve if drift velocity is known and I=nAvq for all charge carriers | |
| 590255512 | electrical power(W) | = VxI = (IxI)R = (VxV)/R | |
| 590255513 | power dissipation | rate at which energy is transferred to an element in a circuit | |
| 590255514 | work done | = VIt | |
| 590255515 | current in series circuit | is the same everywhere | |
| 590255516 | Kirchoff's first law | The total current into any point in a circuit is equal to the total current out of that point | |
| 590255517 | conservation of charge | results in Kirchoff's law | |
| 590255518 | Kirchoff's second law | The sum of potential rises and falls around a closed path is zero | |
| 590255519 | conservation of energy | energy cannot be created or destroyed, this leads to Kirchoff's second law | |
| 590255520 | resistors in series | R= R1+R2+R3... | |
| 590255521 | resistors in parallel | 1/R = 1/R1 + 1/R2 +... | |
| 590255522 | potential divider | resistors connected in series across a voltage source where V1/V2 = R1/R2 | |
| 590255523 | potentiometer | device used to continuously vary resistance and therefore pd | |
| 590255524 | internal resistance | the resistance to electric current of a source of emf (r), V= terminal pd = E-Ir | |
| 590255525 | electron gas | electrons in a metal are described as making up this | |
| 590255526 | drift velocity | the average velocity of electrons in a conductor with a source of emf connected across it | |
| 590255527 | semiconductors | materials like silicon and germanium which have resistivities between those of insulators and conductors | |
| 590255528 | intrinsic semiconductors | pure semiconductors whose conductivity is unaffected by external factors | |
| 590255529 | hole | positive charge carriers observed in addition to electrons in semiconductors | |
| 590255530 | intrinsic conduction | the simulatneous but opposite movement of electrons and holes in a semiconductor | |
| 590255531 | extrinsic semiconductors | semiconductors which arise from doping, they contain impurities | |
| 590255532 | doping | process of introducing impurities to semiconductor lattice which results in extra charge carriers | |
| 590255533 | donor | an impurity which releases free electrons into an extrinsic semiconductor lattice making it n type (negative type) | |
| 590255534 | acceptor | an impurity which traps electrons in an extrinsic semiconductor making it p type (positive as it has an excess of holes) | |
| 590255535 | insulator | substance which at room temperature has insufficient energy to free electrons from atoms to allow conduction | |
| 590255536 | load | resistance in a circuit | |
| 590255537 | wave-particle duality | anything that has particle properties can be shown to have wave properties too | |
| 590255538 | quantum mechanics | describes motion of very small particles traveling at very high speeds; energy is gained/ lost in packets called quanta (photons for light energy) | |
| 590255539 | photons | particle-like packets of light energy | |
| 590255540 | black body | a perfect emitter and absorber of all wavelengths of radiation | |
| 590255541 | Planck's constant | = E/f | |
| 590255542 | radiation flux | =Power/area | |
| 590255543 | wavicle | a wave-particle object | |
| 590255544 | photoelectric effect | observed phenomena of electrons emitted from a metal irradiated with UV | |
| 590255545 | photoelectrons | electrons emitted from metal atoms in the photoelectric effect | |
| 590255546 | threshold frequency | minimum frequency below which no emission of photoelectrons occur | |
| 590255547 | work function | hf=work function + maximum kinetic energy | |
| 590255548 | electronvolt | energy transferred whwn an electron travels through a pd of 1V | |
| 590255549 | stopping potential | The applied potential difference which just stops emitted photoelectrons reaching the collector electrode | |
| 590255550 | photomultiplier tube | device for amplifying a single photon event by means of electron avalanche | |
| 590255551 | spectrometer | device used to separate wavelengths in a beam of radiation | |
| 590255552 | line spectra | Shows only lines specific to wavelengths present (Neon sign) shows bars of colors | |
| 590255553 | continuous spectra | full spectrum of radiation emitted by black body | |
| 590255554 | emission spectra | spectra produced when electrons are given energy to reach high energy levels which is emitted as light when electrons return to lower levels | |
| 590255555 | absorption spectra | dark line spectra produced when atoms in a substance absorb particular wavelengths of radition | |
| 590255556 | ground state | the state in which an atom has least energy (n=1) | |
| 590255557 | ionisation | when an electron is given enough energy to escape, the atom transition is n=1 to n= infinity | |
| 590255558 | excitation | electron moving from a lower to higher energy state | |
| 590255559 | Franck and Hertz | Experiment which was used to determine excitation energies of mercury | |
| 590255560 | laser | device used to produce intense coherent beam of light by stimulating atoms | |
| 590255561 | photovoltaic cells | devices whcih produce a current through the interation of light photons with semiconductor materials | |
| 590255562 | efficiency | = useful energy/ total energy x 100% |
