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Question: White light is incident normally on a glass surface (n = 1.52) that is coated with a film of MgF<sub...

White light is incident normally on a glass surface (n = 1.52) that is coated with a film of MgF2 (n = 1.38). For what minimum thickness of the film will yellow light of wavelength 550 nm (in air) be missing in the reflected light –

A

99.6 nm

B

49.8 nm

C

19.6 nm

D

10.6 nm

Answer

99.6 nm

Explanation

Solution

2t = λn\frac{\lambda}{n}

Ž For tmin m = 0

tmin = λ4n\frac{\lambda}{4n}= 5.5×10−74×1.38\frac{5.5 \times 10^{- 7}}{4 \times 1.38}= 99.6 nm