Question

The electron in the hydrogen atom jumps from excited state n = 3 to ground state n = 1. The photon thus emitted radiate a photosensitive material. If the work function of the material is 5.1 eV the stopping potential of the photosensitive material is given by

(1) 5.1 V

(2) 17.2 V

(3) 7 V

(4) 12.1 V

Answer 1

(3) 7 V

When a transition take place from state n = 3 to n = 1, the energy of photon emitted is

Let V_s be the stopping potential of the photo sensitive material. Then according to Einstein’s photoelectric equation we must have