Question

What minimum separation between two parallel plates of glass (nglass =1.5) produces constructive interference for the reflected light with a 710 nm wavelength if the gap between the plates is filled with oil with noil =1.8?

Answer 1

Answer:

The  value is  $t = 9.861 *10^{-8} \ m$

Explanation:

From the question we are told that

   The  refractive index of glass is $n_{glass} = 1.5$

     The wavelength is  $\lambda = 710 nm = \frac{710}{1 * 10^9} = 710*10^{-9} \ m$

      The  refractive index of  oil is  $n_{oil} = 1.8$

Generally the condition for refractive index is  mathematically represented as

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

Where  t is the separation between two parallel plates of glass , now at minimum  m which is the  order of maxima produced is   =  0

So

     $2 * t = [0 + \frac{1}{2} ] \frac{710 *10^{-9}}{1.8}$

    $t = 9.861 *10^{-8} \ m$