Question

A lens with a refractive index of 1.5 is coated with a material of refractive index 1.3 in order to minimize reflection. If λ denotes the wavelength of the incident light in air, what is the thinnest possible such coating?

Answer 1

Answer:

0.1923  λ

Explanation:

t = thickness of the coating material applied over the lens

n = index of refraction of the coating material = 1.3

m = minimum order = 0

λ = wavelength of the incident light

For destructive interference , the condition is given as

2 n t = (m + (0.5)) λ

Inserting the values

2 (1.3) t = (0 + 0.5) λ

t = 0.1923  λ