Physics-
General
Easy
Question
When a point source of monochromatic light is at a distance of 0.2 m 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
- The stopping potential will be 0.2 V
- The stopping potential will be 0.6 V
- The saturation current will be 6 mA
- The saturation current will be 18 mA
The correct answer is: The stopping potential will be 0.6 V
Cut off voltage is independent of intensity and hence remains the same. Since distance becomes 3 times, so intensity (I) becomes 
Hence photo current also decreases by this factor i.e. becomes 
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