A lens that has an index of refraction of 1.61 is coated with a non-reflective coating that has an index of refraction of 1.45. Determine the minimum thickness for the film if it is to be non-reflecting for light of wavelength 5.60 × 10²nm. A)1.93 × 10^-⁷ m B)3.86 × 10^-⁷ m C)4.83 × 10^-⁸ m D)9.66 × 10^-⁸ m E)8.69 × 10^-⁸ m

Question

Quizplus · Accepted Answer

The minimum thickness for destructive interference in a non-reflective coating is given by $ t = \frac{\lambda}{4n} $, where $ \lambda $ is the wavelength in the medium and $ n $ is the index of refraction of the coating. The wavelength in the coating is $ \lambda/n $, so $ t = \frac{560 \, \text{nm}}{4 \times 1.45} = 9.66 \times 10^{-8} \, \text{m} $.

A Lens That Has an Index of Refraction of 1