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, thenThe stopping potential will be 0.2 VThe stopping potential will be 0.6 VThe saturation current will be 6 mAThe saturation current will be 18 mA ​

Solution

## The correct option is B The stopping potential will be 0.6 VCut off voltage is independent of intensity and hence remains the same. Since distance becomes 3 times, so intensity (I) becomes 19. Hence photo current also decreases by this factor i.e. becomes 189=2mA.

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