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 0.6volt and 18 mA resp.
if the same source is placed 0.6 m away from the photoelectric cell then find the new stopping potential and saturation current.

Hi User name,

Please find below the solution to the asked query:

the stopping potential depends on the frequency of the light used and as the incidnt light is same in both the case the stopping potential will remain the samei.e. Vs = 0.6 voltswhile as intensity is inversly proportional to square of distance from the light source so when the distance has been tripled as original position = 0.2 m, while final position is 0.6 m , which is three thimes the original distance hence the intensity  and the saturation current will decrease by 132 timehence the new saturation current will be 1 9×18 = 2mA
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