Question

Define the terms (i) 'cut-*** voltage' and (ii) 'threshold frequency' in relation to the phenomenon of photoelectric effect.

Using Einstein photoelectric equation show how the cut-** voltage and threshold frequency for a given photosensitive material can be determined with the help of a suitable plot/graph.

Answer 1

(i) Cut-* voltage :** The minimum negative potential (V0) applied to the plate or anode (A) for which the photoelectric current just becomes zero.

(ii) Threshold frequency : The minimum frequency of incident radiation which is required to have photoelectrons emitted from a given metal surface.

Hence the intercept, on the Y - axis, gives v0. (one can read V0, for any v, from the graph)