Question

A camera lens (n = 1.50) is coated with a thin film of magnesium fluoride (n = 1.38) of thickness 120.0 nm. What wavelength in the visible spectrum is most weakly transmitted through the film?

Answer 1

Answer:

 662 nm

Explanation:

given,

camera lens of n = 1.5

magnesium fluoride n = 1.38

thickness  = 120 n m = 120 × 10⁻⁹m

thickness = $\dfrac{wavelength}{4 \times \ refractive\ index}$

         $120\times 10^{-9}= \dfrac{wavelength}{4 \times 1.38}$

wave length = 120× 10⁻⁹ × 4 × 1.38

                     = 0.662 × 10⁻⁶ m

                     = 662 nm

hence, the wavelength is equal to  662 nm