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.

Options

A. 100 nm
B. 50 nm
C. 200 nm
D. 25 nm

Answer

A

Explanation

Condition for constructive interference is
`2mut=[2n+1](lamda)/(2)`
where, `n=0,1,2,3,…`
For minimum thickness, `n=0`
`2mut=(lamda)/(2)`
`impliest=(lamda)/(4mu)=(400xx10^(-9))/(4xx1.5)=100nm`