Question

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

• A. Stopping potential will be $0.2V$
• B. Stopping potential will be $0.6V$
• C. Saturation current will be $6mA$
• D. Saturation current will be $2mA$

Answer 1

Answer: (B), (D)

Saturation current will be $2mA$

Stopping potential does not depend on distance between source & cell (i.e., intensity) and saturation current depends on Intensity

$(I\propto \frac{1}{r^2})$

$\therefore I=18\frac{{\left(0.2\right)}^2}{{\left(0.6\right)}^2}$

$I=2mA$