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A material having an index of refraction...

A material having an index of refraction of 1.30 is used as an antireflective coating on a piece of glass `(n = 1.50). What should be the minimum thickness of this film in order to minimize reflection of 500 nm light?

Text Solution

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Treating the anti-reflectance coating like a camera lens coating,
`2 t = (m + (1)/(2)) (lambda)/(n)`
Let `m = 0: t = (lambda)/(4n) = (3.00cm)/(4(1.50))= 0.500 cm`
This anti-reflectance coating could be easily countered by changing the wavelength of the radar to 1.50 cm - now creating maximum reflection.
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