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

Explanation

(i) Cut-off voltage : The minimum negative potential (`V_(0)`) 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.
As per Einstein.s photoelectric equation
`eV_(0)= vh-hv_(0)`, for `v gt v_(0)`
`V_(0)=(h)/(e)(v-v_(0))`
Hence the intercept, on the Y - axis, gives `v_(0)`. (one can read `V_(0)` for any v, from the graph)