Question

Two plates, one of thickness ?1 = 3.8 mm and the other
of thickness ?2 = 9.0 mm, are manufactured of a certain substance.
When placed alternatively in the way of monochromatic light, the first
plate transmits ?1 = 0.84 fraction of luminous flux and the second one,
?2 = 0.70. Find the coefficient of linear absorption of that substance.
Light falls at right angles to the plates. Neglected secondary reflections.

Answer 1