According to Einstein's photoelectric equation, EK=E−φ0 where, EK= kinetic energy, E= energy of incident photon and φ0= work function of metal surface. ⇒‌‌E=EK+φ0 ....(i) When energy of incident photon is increased by 20%, then
E′=E+20% of E=E+‌
20
100
E=‌
6E
5
⇒‌‌E′=1.2E
∴‌‌EK′=E′−φ0⇒E′=EK′+φ0
1.2E=EK′+φ0...(ii) From Eqs. (i) and (ii), we get ‌