Assertion : A $p-n$ junction with reverse bias can be used as a photo-diode to measure light intensity. Reason : In a reverse bias condition the current is small but it is more sensitive to change in intensity of incident light.

• Correct answer
  A

  If both assertion and reason are true and reason is the correct explanation of assertion.
• B

  Ifboth assertion and reason are true but reason is not the correct explanation of assertion.
• C

  If assertion is true but reason is false.
• D

  If both assertion and reason are false.

Hence, the correct answer is option: 'A'.