When a monochromatic point source of light is at a distance of `0.2` m from a photoelectric cell, the cut off voltage and the saturation current are respectively `0.6V` and `18.0 mA` if the same source is placed `0.6 m` away from the photoelectric cell , then

Options

A. the stopping potential will be `0.2` volt
B. the stopping potential will be `0.6` volt
C. the saturation current will be `6.0mA`
D. the saturation current will be `2.0mA`

Answer

b,d

Explanation

Since inetensity of incident light `I prop1//r^(2)`, therefore on increasing the distance `0.2m` to `0.6m`, i.e three times, the intensity of the incident light reduce to `1//9` times the original intensity. But energy of each photon will still remain the same. The value of cut off potential is independent of the intensity of the incident light but dependece upon the frequency of the incident light. The saturation current depends upon the intensity of the incident light and not on energy of the incident light.