Question

Monochromatic light of wavelength, lambda, is traveling in air. The light then strikes a thin film having an index of refraction, n1 that is coating a material having an index of refraction n2. If n1 is larger than n2, what minumim film thickness will result in minimum reflection of this light?A. lambda/(4*n2)B. lambda/n2C. lambda/4D. lambda(2*n1)E. lambdaF. lambda/(2*n2)G. lambda/n1H. lambda/(4n1)I. lambda/2

Answer 1

The correct option is H

Step-by-step explanation:

From the question we are told that

The index of refraction of coating is
`n_1`

The index of refraction of material is
`n_2`

Generally the condition for constructive for a thin film interference is mathematically represented

`2 * t = [ m + (1)/(2)] (\lambda)/(n_1 )`

Here t represents the thickness

For minimum thickness m = 0

So

`2 * t =0 + (1)/(2)(\lambda)/(n_1 )`

=>
`t =(\lambda)/(4n_1 )`