Question

What is the thinnest film of a coating with n = 1.40 on glass (n=1.52) for which destructive interference of the red component (650 nm ) of an incident white light beam in air can take place by reflection?

Answer 1

The thinness of film is 116 nm.

Step-by-step explanation:

Given that,

Wavelength = 650 nm

Refractive index = 1.40

We need to calculate the thickness

Using formula of thickness for destructive interference

`2nt=(m+(1)/(2))\lambda`

Here, m = 0

`2nt=(1)/(2)\lambda`

`t = (1)/(4)*(650*10^(-9))/(1.40)`

`t=1.16*10^(-7)\ m`

`t = 116\ nm`

Hence, The thinness of film is 116 nm.