Assertion(A): Corpuscular theory fails in explaining the velocities of light in air and water.

Reason(R): According to corpuscular theory, light should travel faster in denser media than is rarer media.

One of the key aspects where corpuscular theory faced challenges was in explaining the phenomenon of refraction, which involves the change in direction and speed of light as it passes from one medium to another. The corpuscular theory could not adequately account for the observed behavior of light during refraction, particularly the relationship between the change in velocity and the change in direction.