Thickness of film for minimum density

Question

A lens ( =1.5) is coated with a thin film of refractive index 1.2 in order to reduce the reflection from its surface at $\lambda$ = 4800 Å. Find the minimum thickness of the film which will minimize the intensity of the reflected light.

I am not getting , how to start it . How to visualise it .

Can anybody provide me hint

Comments

-1. Start by reading the worked solution in the back of the book! Then copy it into your exercise book!   :)

Do you actually have a difficulty with the printed solution? If not, I do not understand why you have asked the question, posted the printed solution, then voted it the best answer.

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This solution is not provided in my book . I found it on internet.
After posting the question , I found it on internet  .
If anyone can provide a better answer , I will choose it as best answer .

Answer 1