1.3 photons

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  • Created by: maddie
  • Created on: 29-11-12 09:32
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  • photons
    • Light - small part of spectrum of electromagnetic (EM) waves, our eyes cannt detect other parts.
    • In vaccum all EM waves travel at speed of light, c (3.0x1068 ms). Wavelength = c/ frequency,f.
      • waveleght expressed in nanometers, 1nm = 10^-9 m.
    • EM waves - electric and magnetic waves whcih travel together and vibrate they are ...
      • at right angles to each other and the direction they are travelling
      • in phase with each other , reach peak at same time.
    • EM waves are emitted by a charged particle when it loses energy when ...
      • fast moving electron stops, slows down or change direction
      • electron in shell of atom moves to different shell of lower energy
    • EM waves emitted as short burst of waves leaving source in different direction. Each burst is a packet of EM waves - a PHOTON
      • photon theory established by einstein to expalin photoelectrcity - emission of electrons from metal surface when light directed at surface
        • Einstein assumed energy, E, of a photons depends on its frequency: E=hf, where h - placks constant, 6.63 x10^-34Js.
    • laser beam consists of photons of same frequency
      • power of laser beam - energy/sec transfered by photons. Power of beam = nhf where...
        • f = frequency of photons, n = number of photons passing fixed point per sec, h = plancks constant


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