Question

What is the minimum thickness of thin film required for constructive interference in the reflected light through it ?
(Given, the refractive index of the film `=1.5,` wavelength of the lilght incident on the film `=600` nm.
A. `100 nm`
B. `150 nm`
C. `200 nm`
D. `250nm`

Answer 1

Correct Answer - B
`2 mu t cos r = (2n + 1) (d)/(2)` for minimum thickness `t = (lambda)/(4 mu cos r) = 150 nm`