Numerical Problem on Thin Film interference ::::: Engineering Physics::::: @balendra

Numerical Problem on Thin Film interference for Engineering Physics and B.Sc. Physics Students Question: A parallel beam of light ($\lambda = 5890\times10^{-8} cm$) is incident on a thin glass plate ($\mu =1.5$) such that the angle of refraction into the plate is 60$^{o}$. Calculate the smallest thickness of the glass plate which will appear dark by reflection?