Question

On a photosensitive surface, if the intensity of incident radiation is increased, the stopping potential

• A. first increases and then decreases
• B. decreases
• C. increases
• D. remains unchanged

Hint:

Stopping potential is a measure of maximum kinetic energy of photoelectrons. It depends on frequency of light, not intensity. Intensity changes the saturation current, not the stopping potential.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
We need to know how stopping potential in photoelectric effect varies with intensity of incident radiation.

Step 2: Key Formula or Approach:
Einstein’s photoelectric equation: \(K_{\text{max}} = h\nu - \phi = eV_0\), where \(V_0\) is stopping potential. \(K_{\text{max}}\) depends only on frequency \(\nu\) of incident light, not on intensity. Intensity only affects the number of photoelectrons (photocurrent).

Step 3: Detailed Explanation:
Increasing intensity means more photons per second, hence more electrons emitted, but their maximum kinetic energy (hence stopping potential) does not change because each photon’s energy depends only on frequency. Thus stopping potential remains unchanged.

Step 4: Final Answer:
Option (D) remains unchanged.