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: Read the question.
We shine light on a metal surface and then make the light brighter (more intense). We must say what happens to the stopping potential.

Step 2: Recall the key equation.
Einstein's photoelectric equation is $K_{\max} = h\nu - \phi = eV_0$, where $V_0$ is the stopping potential.

Step 3: See what controls the energy.
The maximum kinetic energy of the escaping electrons depends only on the frequency $\nu$ of the light and the work function $\phi$, not on how bright the light is.

Step 4: Think about what intensity does.
Brighter light just means more photons arrive each second, so more electrons come out. That raises the current, not the energy of each electron.

Step 5: Connect to stopping potential.
Since the top electron energy does not change, the voltage needed to stop them, $V_0$, also does not change.

Step 6: State the result.
The stopping potential stays the same when intensity is increased.
\[ \boxed{\text{remains unchanged}} \]