Given below are two statements: one is labelled as Assertion (A)...

Intensity $I$ is defined as the energy incident per unit area per unit time. Therefore, the total energy $E$ incident on a surface of area $A$ in time $t$ is given by $E = IAt$.

For a completely absorbing surface, the entire incident energy is absorbed. The momentum $p$ transferred by an electromagnetic wave is related to its energy $E$ by the relation $p = \dfrac{E}{c}$, where $c$ is the speed of light.

Substituting the expression for energy, we get $p = \dfrac{IAt}{c}$.

Thus, both Assertion (A) and Reason (R) are true, and Reason (R) provides the correct logical derivation for Assertion (A).

Answer: Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).