Question

Plot a labelled graph of |Vs| where Vs is stopping potential of photoelectrons versus frequency 'f' of incident radiation. How will you use this graph to determine the value of Planck's constant? Explain.

Answer 1

Graph of stopping potential of photoelectrons versus frequency of incident radiation is shown below:

_eV₀ = h(v - v₀)

V₀ = \(\frac{h}{e}v-\frac{h}{e}v_0\)

Slope of the graph = h/e (∵ e is charge on electron)

∴ h = slope of the graph x e

By measuring the slope of the straight line obtained and using the value of 'e' the value of planck's constant can be calculated.