Question

For photoelectric effect in sodium, the figure shows the plot of cut-*** 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 photoelectron is zero.

∴ From fig. threshold frequency

v0 = 4.5 × 1014 Hz

(ii) Work function, W = hv0

= 6.6 × 10–34 × 4.5 × 1014 joule

= (6.6 x 10-34 x 4.5 x 1014/1.6 x 10-19 ev)

= 1.85 eV