Waves, Light & Quanta
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Transcript of Waves, Light & Quanta
4
Diffraction grating
x
d
y
s
a
• place secondary sources along wavefront
• ...and trigger when wavefront arrives
• apply to sinusoidal waves by taking into account the phase with which components arrive• combine by adding the amplitudes
• contributions may therefore interfere constructively or destructively
INTERFERENCE
7
Michelson interferometer
• interference by division of amplitude
beamsplitter detector
source
δx δx
Michelson interferometer
• interference by division of amplitude
beamsplitter detector
source
δx δx
• sodium doublet
optique-ingenieur.org
chemistry.oregonstate.edu
• FTIR: Fourier transform infrared
9
Newton’s rings
diffuser
beam-splitter
lens
plate
s
r
• apply to sinusoidal waves by taking into account the phase with which components arrive• combine by adding the amplitudes
• contributions may therefore interfere constructively or destructively
www.sciencebuddies.org
13
Coherence
NON-POINT OBJECTS• many independent emitters, e.g. different atoms in
star• spatial extent (angular width) determines fringe visibility• partial visibility when phase difference partially defined• coherence is a measure of extent to which the phase difference is known
• degree of coherence 2
221
2112
EE
EE
• (approximate expression – requires complex numbers)
• complex degree of coherence
2211
2112
EEEE
EE
14
Light and optics
RAYS• straight propagation paths
• least time (Fermat’s principle)
• reflection, refraction, lenses, telescopes, microscopes
WAVES• Huygens’ description of propagation, reflection,
refraction• polarization, colour (wavelength, frequency)
• diffraction, interference, beats, interferometers
directrix
focus
PHOTONS• Planck, Compton, Einstein
• Maxwell’s electromagnetism, Einstein’s relativity