Assertion :The principle of reversibility presupposes that the attenuation of a light ray during its passage through an optical medium because of reflection, refraction, and absorption is not affected by a reversal of the direction of the ray. Reason: Principle of reversibility can only be applied to lens system.

The correct option is C Assertion is correct but Reason is incorrect
Principle of reversibility states that when final path of a ray of light after any number of reflections and refractions is reversed, the ray retraces its entire path or in simple words, light follows exactly the same path if its path of travel is reversed. It has no effect on the attenuation of light ray. So, the assertion statement is true.

Principle of reversibility can be applied to lens system as well as the mirror system. So, the reason statement is incorrect.