Question

When a point source of monochromatic light is at a distance of 0.2m from a photoelectric cell, the cut-off voltage and the saturation current are 0.6 volt and 18 mA respectively. If the same source is placed 0.6 m away from the photoelectric cell, then

• A. The stopping potential will be 0.2 V
• B. The stopping potential will be 0.6 V
• C. The saturation current will be 6 Ma
• D. The saturation current will be 18 mA

Answer 1

Answer: (B)

The stopping potential will be 0.6 V

Answer 2

Photoelectric current (i) ∝ Intensity ∝ .

If distance becomes 0.6 m (i.e. three times) so current becomes $\frac { 1 } { 9 }$times i.e. 2mA.

Also stopping potential is independent of intensity i.e. it remains 0.6 V