Experimental Study of Photoelectric Effect

Physics

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Effect of potential on photocurrent

Photoelectric current is zero when the stopping potential is sufficient to repel even the most energetic photoelectrons with the maximum kinetic energy so that
For a given frequency of the incident radiation, the stopping potential is independent of its intensity.

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Dependence of intensity on photocurrent

When the intensity of light is increased the saturation current also increases. It is shown in the figure given here. let the intensities be in the order
Then the saturation current

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Dependence of photo current on frequency of light

The saturation current depends on the intensity of light, not on frequency. Hence no matter how much is the frequency for the same intensity of light, the saturation photocurrent will be same.

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Dependence of stopping potential of light on frequency of light

For a particular frequency of incident radiation, the minimum negative (retarding) potential given to the plate A for which the photocurrent stops or becomes zero is called the cut-off or stopping potential.
We now take three different lights at different frequencies , , but of same intensity. More the frequency of light, more negative potential is needed to stop the photocurrent. Hence the stopping potential increases. Hence as shown in the figure, the magnitude > >  

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Observations on Photo Electric Effect

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