Question

An electron in the hydrogen atom jumps from excited state n to the ground state. The wavelength so emitted illuminates a photosensitive material having work function 2.75 eV. If the stopping potential of the photoelectron is 10 V then the value of n is

(a) 2

(b) 3

(c) 4

(d) 5

Answer 1

The correct option is (c) 4.

Explanation:

Here, Stopping potential, V_o = 10V 

Work function, W = 2.75 eV 

According to Einstein's photoelectric equation 

eV_o = hv - W or hv = eV_o + W

= 10 eV + 2.75 eV = 12.75 eV .......(i) 

When an electron in the hydrogen atom makes a transition from excited state n to the ground state (n =1), then the frequency (v) of the emitted photon is given by