Question

A point source of light is used in a photoelectric effect. If the source is moved farther from the emitting metal, then the stopping potential

• A. will increase
• B. will decrease
• C. will remain constant
• D. will either increase or decrease

Hint:

Stopping potential depends on the frequency of light and the metal, not on the intensity.

Answer 1

The Correct Option is C

Step 1: Photon energy
Each photon carries energy $h\nu$, fixed by the source frequency, not by its distance.

Step 2: What intensity changes
Lower intensity means fewer photons per second, so the photocurrent falls.
The maximum kinetic energy of an emitted electron $K_{max}=h\nu-\phi$ stays the same.

Step 3: Result
$V_0=\dfrac{K_{max}}{e}$ is unchanged, so option (C) is correct.

Final Answer:
The stopping potential stays the same. \[ \boxed{\text{(C) }\text{will remain constant}} \]