Problem 5.215

A beam of monochromatic light passes through a pile of $N=5$ identical plane-parallel glass plates each of thickness $l$ $=0.50 \mathrm{~cm} .$ The coefficient of reflection at each surface of the plates is $\rho=0.050 .$ The ratio of the intensity of light transmitted through the pile of plates to the intensity of incident light is $\tau=0.55$. Neglecting the secondary reflections of light, find the absorption coefficient of the given glass.