# A nonreflective coating of magnesium fluoride (n =1.38) covers the glass (n = 1.52) of a camera lens. If the coating prevents the reflection of yellow-green light (`lambda` = 565 nm), determine the...

A nonreflective coating of magnesium fluoride (n =1.38) covers the glass (n = 1.52) of a camera lens. If the coating prevents the reflection of yellow-green light (`lambda` = 565 nm), determine the minimum nonzero thickness of the coating.

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### 1 Answer

A non-reflective coating of magnesium fluoride (n =1.38) covers the glass (n = 1.52) of a camera lens. The coating prevents the reflection of yellow-green light with a wavelength `lambda = 565*10^-9 m ` .

The minimum thickness of the coating required to accomplish this is required. If the minimum thickness if `t_min` , it is given by the formula `t_min = lambda/(4*n)` , where n is the refractive index of the non-reflective coating which is 1.38

Substituting `lambda = 565*10^-9` m and `n = 1.38`

`t_min = (565*10^-9)/(4*1.38) = 102.35*10^-9 m`

The minimum thickness of the non-reflective coating on the camera lens to prevent of reflection of light with a wavelength of 565 nm is 102.35 nm.

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