Reflections from a thin layer of air between two glass plates cause constructive interference for a particular wavelength of lig

Question

3 years ago

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Reflections from a thin layer of air between two glass plates cause constructive interference for a particular wavelength of lig

ht λ. By how much must the thickness of this layer be increased for the interference to be destructive?
A. λ/8
B. λ/4
C. λ/2
D. λ

Physics

1 answer:

gavmur [86] · Answer 1 · 2022-02-05T23:13:44+03:00

Answer:

C

Explanation:

Thin film interference is most constructive or most destructive when the path length difference for the two rays is an integral or half-integral wavelength, respectively. That is, for rays incident perpendicularly, 2t = λn, 2λn, 3λn, . . . or 2t = λn/2, 3λn/2, 5λn/2 , .....

We see a constant phase shift off λn/2. Hence option C