Question

For photoelectric effect in sodium, the figure shows the plot of cut-off voltage versus frequency of incident radiation.Calculate.
(i) Threshold frequency
(ii) Work function for sodium

Answer 1

(i) The threshold frequency is the frequency of incident light at which kinetic energy of ejected threshold is zero.
$\therefore$From fig, threshold frequency,
$v_0=4.5\times {10}^{14}Hz$

(ii) Work function, $W=h{v}_0$
$=6.6\times {10}^{-34}\times 4.5\times {10}^{14}$joule
$=\frac{6.6\times {10}^{-34}\times 4.5\times {10}^{14}}{1.6\times {10}^{-19}}=1.85eV$