Question

A nonreflective coating (n = 1.34) covers the glass (n = 1.52) of a camera lens. Assuming that the coating prevents reflection of a specific wavelength (vacuum = 554 nm), determine the minimum nonzero thickness that the coating can have.

Answer 1

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A nonreflective coating (n = 1.34) covers the glass (n = 1.52) of a camera lens. Assuming that the coating prevents reflection of a specific wavelength (vacuum = 523 nm), determine the minimum nonzero thickness that the coating can have.   

answer

there are phase changes for the reflection of the light incident from the air (n=1) to the coating(n=1.34), and for the reflection of the light incident from the coating(n=1.32) to the glass (n=1.52). Hence these two phase change cancel one another. We only need to make the traveling of the light inside the coating to be of half the wavelength. That is: the minimum nonzero thickness of the coating is: 523 nm/(4n) = 523 nm/(4*1.34) = 97.57nm