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Draw a graph, showing the effect of potential on photoelectric current. Hence define stopping potential. |
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Answer» Solution :Effect of potential on photoelectric current. Light of fixed intensity `I_(1)`and FREQUENCY v be made to fall on photosensitive plate. The electrode C is made negative so that the current becomes zero. Let it be `V_(0)`(called stopping potential). Now the potential of C is increased in steps and a graph is plotted. The graph is as shown in the figure.  If the same experiment is repeated with radiation having intensity `I_(2) (I_(2) GT I_(1))` the SATURATION current will be higher but stopping potential is the same. It means that stopping potential is independent of intensity of incident radiations. The retarding potential, `V_(0)`for which the photoelectric current just becomes zero is called stopping potential or cut-off potential. If mass of electron is m, charge e and MAXIMUM velocity is `v_("max")` then : `1/2 mv_("max")^(2) = eV_(0)` And `v_("max") = sqrt((2eV_(0))/m)`. |
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