Assertion $(A)$: Photoelectric effect demonstrates the wave nature of light.
Reason $(R)$: The number of photoelectrons is directly proportional to the frequency of light.

• A
  Both $(A)$ and $(R)$ are true and $(R)$ is the correct explanation of $(A)$.
• B
  Both $(A)$ and $(R)$ are true but $(R)$ is not the correct explanation of $(A)$.
• C
  $(A)$ is true but $(R)$ is false.
• D
  Both $(A)$ and $(R)$ are false.