1.5 1.5 1.3 Film 1.3 Fillm Filan 1.3 1.4 1.5 10. The figure above shows three si

Question

1.5 1.5 1.3 Film 1.3 Fillm Filan 1.3 1.4 1.5 10. The figure above shows three situations in which light reflects almost perpendicularly from the top and bottom surfaces of a thin film, with the indices of refraction as shown. For a film to appear dark, the waves represented by rays 1 and 2 must be out ofphase. This can arisefrom phase shifts associated with the reflection at the top and bottom surfaces of the film and the extra distance traveled by ray 2 as it moves through the film (a) For which situation(s) is there a net phase shift (due to reflection) between waves 1 and 2 that is equivalent to either zero wavelengths or one wavelength (?/in ) (that is, a net phase shift of zero or 180°), where ?,1,, is the wavelength of the light in the film? (b) For which situation(s) will the film appear dark when the thickness of the film is equal to h? Film (c) For all 3 situations, write the relation between thickness and wavelength for constructive and destructive interference

Explanation / Answer

a) The question is actually asking for if film will appear bright. YES, it will in both cases A and B. as we can clearly see a net shift of zero in case (A) and (C)

b) The film will appear dark in case (B) as the waves would result in disturbance interference

c) For destructive interference, it would also occur with the film thickness being equal to 1 wavelength of the wave in the film, or 1.5 wavelengths, 2 wavelengths,

For constructive, film thickness is 1/4 wavelength, 3/4 wavelength, 5/4,

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