Define the terms (i) ‘cut-off voltage’ and (ii) ‘threshold frequency’ in relation to the phenomenon of photoelectric effect.
Using Einstein’s photoelectric equation shows how the cut-off voltage and threshold frequency for a given photosensitive material can be determined with the help of a suitable plot/graph.

Solution

i) Cut-off or stopping potential is that minimum value of negative potential at anode which just stops the photo electric current.

ii) The minimum frequency of light below which no photo electric emission will take place is known as threshold frequency.

Now using Einstein’s photoelectric equation, we have

Clearly, V_o – $straight nu$ graph is a straight line.

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