Question

What is the minimum thickness of coating which should be placed on a lens in order to minimize reflection of 566 nm light? The index of refraction of the coating material is 1.46 and the index of the glass is 1.71.

Answer 1

Answer:

The  thickness is   $t = 1.415 *10^{-7 } \ m$

Explanation:

From the question we are told that

    The wavelength is  $\lambda = 566 \ nm = 566 *10^{-9} \ m$

     The  index of refraction of glass is  $n_g = 1.71$

     The index of refraction of the coating is  $n= 1.46$

Generally the condition for destructive interference is  

         $2 t = (m + \frac{1}{2} ) * \frac{\lambda }{n }$

Here m is the order of the interference pattern and given from the question that we are considering minimizing  reflection  m = 0

t = thickness of the coating

substituting values

         $2 t = (0 + \frac{1}{2} ) * \frac{ 566 *10^{-9}}{ 1.46 }$

    =>    $t = 1.415 *10^{-7 } \ m$