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Interferometers - examination of a shadow under a bright...

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Interferometers Interferometers are devices that employ the effects of interference to make very accurate measurements. The most famous of these is called a Michelson interferometer, which was used to measure the wavelength of lines in atomic spectra. Figure %: A Michelson Interferometer The light from a source is split into two by a beamsplitter, half traveling to the right towards the mirror M 1 and half upwards towards the mirror M 2 . Both beams reflect back from the mirrors to the beamsplitter. Part of each of the two beams from M 1 and M 2 are reflected downwards and are reunited as they head towards the detector. The interference pattern will depend on the difference in the path length of the two beams, which can be adjusted by moving the mirror M 1 further away from or closer to the beamsplitter. The nature of the interference pattern at the detector can be used to deduce the wavelength of the light. Diffractive Effects Diffraction occurs whenever a portion of a wavefront is obstructed by some opaque object. Close
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Unformatted text preview: examination of a shadow under a bright source will reveal that it is made up of finely spaced bright and dark regions. In this case, light appears not to be propagating in a straight line; the obstacle alters the amplitude or phase of the light waves such that the regions of the wavefront that propagate beyond the obstacle will interfere with each other. It is crucial to remember that there is no physical difference between interference and diffraction. In general interference concerns situations where only a few waves are interfering, while diffraction concerns a large number of interfering waves. This distinction is arbitrary. Diffraction occurs with other sorts of waves too. Water waves or sound waves, for example spread out after they go through a narrow aperture, or bend into the 'shadow' region behind an obstacle. Figure %: Diffraction of water waves....
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