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A glass lens, n glass = 1.52 , has a 131 nm thick antireflective film coating one side, n film = 1.25. White light, moving through the air,
Question
A glass lens, n glass = 1.52 , has a 131 nm thick antireflective film coating one side, n film = 1.25. White light, moving through the air, is perpendicularly incident on the coated side of the lens. What is the largest wavelength of the reflected light that is totally removed by the coating?
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Physics
4 years
2021-07-20T06:39:07+00:00
2021-07-20T06:39:07+00:00 1 Answers
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Answers ( )
Answer:
655 nm
Explanation:
When the intereference is destructive then the thickness, d of antireflective film coating one side is given by
2d=w/2n
Where w is wavelength and n is the reflective index of the film
Making w the subject of formula then
w=4nd
Substituting 1.25 for n and 131 nm for d then the wavelength will be
w=4*1.25*131=655 nm
Therefore, the wavelength is equivalent to 655 nm