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What should the index of refraction of the coating be if it must cancel 600-nm light that hits the coated surface at normal incidence?

a) 1.5
b) 1.8
c) 2.0
d) 2.5

1 Answer

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Final answer:

Theanswer is Option C, index of refraction of the coating should be 2.0 to cancel 600-nm light that hits the coated surface.

Step-by-step explanation:

The index of refraction of the coating must cancel 600-nm light that hits the coated surface at normal incidence. We can use the formula for destructive interference, which is given by:

n⁻¹λ = 2d

Where n is the index of refraction of the coating, λ is the wavelength of light, and d is the thickness of the coating. Rearranging the formula, we get:

n = 2d/λ

Substituting the values, we find:

n = 2 * 600 nm / 600 nm = 2.0

Therefore, the index of refraction of the coating should be 2.0 to cancel 600-nm light that hits the coated surface.

However, if we consider a scenario where the film is quarter-wavelength thick, then the refractive index that would lead to destructive interference for 600-nm light can be determined. For a quarter-wavelength film, we would look for a condition where the film's optical thickness is 600 nm / 4 = 150 nm. The index of refraction for this scenario would be n = λ/4t, where λ is the vacuum wavelength of the light, and t is the thickness of the film.

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