Question

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.

Answer 1

We have,

eV₀ = hv -φ₀; 

V₀ = stopping potential 

Or, V₀ = \(\frac{h}{e}v\) - \(\frac{φ_0}{e}\) 

∴V₀ ∝ v 

∴ v Vs V₀ graph is a straight line as shown : 

Comparing the above relation with y = mx + c, 

We find the slope of graph is h/e.

The x- intercept is v₀ and y- intercept is \(-\frac{ϕ_0}{e}\).

Thus, 

v₀ and V₀ can be determined.