Physics, asked by rdrdcool, 1 year ago

. Alens is coated with thin films of transparent substance MgF2 (n = 1.38) to reduce reflection from glass surface. How thick a coating is needed to produce minimum reflection at center of visible spectrum (λ = 550nm)?

Answers

Answered by kvnmurty
3
The change in phase due to the optical path length of the light inside the film should be equal to π.    Let t = thickness of the transparent film.
 
 So total optical path length = λ/2 = n * t + n * t    inside the film for the reflected ray.

The reflected rays from both surfaces of the film will be in opposite phase.  So the transmitted rays go through without destructive interference.

t = λ/(4n)  = 550/(4*1.38) = 99.64 nm
  Thickness is  t  or   multiples of  t.

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