Fields, Particles and Frontiers of Physics (OCR Physics A)

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Terms in this set (30)
nucleon numbernumber of neutrons and protons in the nucleus of an atom (a.k.a. mass number)activitythe rate of decay of nuclei in a radioactive sampledecay constantprobability of a decay of a nucleus per unit timehalf lifethe mean time taken for half the number of active nuclei in a radioactive sample to decaybinding energyminimum energy to separate protons and neutrons of a nucleusintensitypower per unit cross-sectional areaFaraday's law of electromagnetic inductioninduced e.m.f. is proportional to the rate of change of magnetic fluxLenz's lawthe induced current or e.m.f. is in a direction so as to produce effects which oppose the change producing itisotopea version of an element with a different number of neutrons (but the same number of protons and electrons)Doppler effectthe change in the frequency and wavelength of a wave caused by the relative movement between source and detectorpiezoelectric effectapplication of a p.d. across a crystal causes a vibrationCompton effectx-ray photon interacts with electron; the scattered photon has a longer wavelength and the electron is ejectedOlber's paradoxif Universe is static and infinite, the night sky should be uniformly bright because every line of sight would end on a starHubble's lawthe speed of recession of a galaxy is proportional to its distancecosmological principleuniverse has the same large-scale structure when observed from any point (homogenous, isotropic and the laws of physics are universal3K microwave background radiationgamma radiation released during the Big Bang has stretched as the Universe expanded, causing it to become microwave with an energy equivalent to a temperature of 3Kcritical densitythe density for which the universe will expand towards a finite limit (resulting in a flat universe)open universeuniverse will expand foreverflat universeuniverse will expand towards a finite limitclosed universeuniverse will contract (to a big crunch)