The diagram shows light incident from above on a film of thickness d. Each of th

Question

The diagram shows light incident from above on a film of thickness d. Each of the three materials in the figure can be chosen to be air, with index of refraction n=1.00, water, with index n=1.33, or glass, with index n=1.50. Under which of the following conditions will the reflected light be completely or nearly eliminated by interference?

(lambda2 refers to the wavelength of the light inside the thin film.)
(Note: In the case that d<<lambda2, you can assume the thickness is so small that the travel distance in material 2 has negligible affect on the phase of the wave. Treat this as if the two interfaces are almost right on top of each other.)

1) d=lambda2/4, material 1 is air, 2 is water, 3 is glass.

2) d<<lambda2, material 1 is air, 2 is glass, 3 is water.

3) d=lambda2/4, material 1 is air, 2 is glass, 3 is water.

4) d=lambda2/2, material 1 is air, 2 is water, 3 is glass.

5) d=lambda2/2, material 1 is glass, 2 is air, 3 is water.

I am not sure if I'm fully understanding phase shifts. I think 1 is true and 2 and 4 are false, but Im not sure. ANY help and an explanation would be Greatly appreciated!!

Explanation / Answer

1) d=lambda2/4, material 1 is air, 2 is water, 3 is glass.

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