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Coherent interference of four sources

Coherent interference of four sources. Grating. A transmission grating is an opaque plate with many closely and regularly-spaced slits on it. It sends light into extremely well-defined directions . When the incident light is white, the forward direction has a white central fringe.

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Coherent interference of four sources

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  1. Coherent interference of four sources

  2. Grating • A transmission grating is an opaque plate with many closely and regularly-spaced slits on it. It sends light into extremely well-defined directions. • When the incident light is white, the forward direction has a white central fringe. • However, the other fringes show a spectrum of colors.

  3. The first interference maximum (fringe) spreads out according to the wavelength of the colors: blue, green, red. Then there is the secondary fringe with various colors. Higher-order fringes usually overlap. • One sees iridescent of colors from a grating.

  4. Reflection Grating • If there are many regularly spaced reflecting surfaces in an array, we have a Reflection Grating (credit card)

  5. Example of Reflection Grating • “Eye” of a peacock feather, • Scales of butterfly wings, • Scales of some snakes, • Beatles

  6. 3-d grating X-ray scattering.

  7. Interferometers • Devices that make accurate measurements by the use of interference. • Split the beam into two and pass one of them through something that can affect the light and then look at the interference pattern to • Measure the speed of the Earth relative to ether. • Measure the air temperature variation. • Measure the gravitational wave…..

  8. Standing Waves---a special example of interference • When two waves with equal frequency and amplitudes travel against each other, they form a standing wave: • Vibration in violin, • Wave from a rope tied to a wall. • The pattern of interference is fixed in space. The destructive interference happens at the nodes and constructive interference happens at the antinodes.

  9. Lippmann Plate: • Mirror surface is coated with a thick layer of fine-grain photographic emulsion. A reflected wave from the mirror interferes with the incident wave to form an interference pattern which is recorded by the emulsion.

  10. Lippmann plate

  11. Interference filter • Two thin films with highly reflective surfaces. • The light in between the film can form standing waves with certain frequency. • The incident wave is transmitted through the films only at this frequency.

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