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Dual Nature of Radiation and Matter — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsDual Nature of Radiation and Matter3 Marks
Question
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.
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Answer

Cut – off voltage: The minimum negative potential$(V_0)$ applied to the plate or anode (A) for which the photoelectric current just becomes zero, Threshold frequency: The minimum frequency of incident radiation which is required to have photo electrons emitted from a given metal surface. As per Einstein's photoelectric equation. $\text{eV}_{0} = \text{hv} - \text{hv}_{0}, \text{ for } \text{v} > \text{v}_{0}$ $\text{v}_{0} = \frac{\text{h}}{\text{e}}(\text{v} - \text{v}_{o} ) $ Hence the intercept, on the v- axis, gives $v_0.$

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