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

Answer:

The  correct option is  H

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

            $2 * t = [ m + \frac{1}{2}] \frac{\lambda}{n_1 }$

Here  t represents the thickness

For minimum thickness  m =  0

So

           $2 * t =0 + \frac{1}{2}\frac{\lambda}{n_1 }$

=>        $t =\frac{\lambda}{4n_1 }$