Question

You are trying to add an anti-reflection coating to a pair of eyeglasses. You know the index of refraction of air is 1.0 and the index of refraction for glass is 1.6. What should the index of refraction of your coating be?

A) 1.2
B) 1.4
C) 1.5
D) 1.6

Answer 1

The ideal refractive index for your anti-reflection coating would be approximately 1.23. However, no real material perfectly matches this value. Option (A), 1.2, is the closest available option.

Step-by-step explanation:

Anti-reflection coatings work by minimizing the reflection of light at the interface between two materials with different refractive indices. Ideally, the coating's index of refraction should be the geometric mean of the air and glass indices:

n_coating = √(n_air * n_glass) ≈ √(1.0 * 1.6) ≈ 1.23

A coating with this index would cause reflected waves from both the air-coating and coating-glass interfaces to destructively interfere, minimizing overall reflection.

Unfortunately, materials with an index of refraction exactly 1.23 are not readily available. Therefore, the best option is to choose a material with an index as close as possible to this ideal value. Option (A), 1.2, is the closest available option among the choices provided. While not perfect, it will still provide significant anti-reflection compared to an uncoated lens.

Option:

(A) is the closest to the ideal index of refraction and would provide the best anti-reflection performance among the given choices.