Sankalp NEET Full Test-5 Question-11 Solution

Question: 11: The light rays having photons of energy 4.2 eV are falling on a metal surface having a work function of 2.2 eV . The stopping potential of the surface is :

(1) 2 eV

(2) 2 V

(3) 1.1 V

(4) 6.4 V

Answer: Option (2)

Explanation:

This question is based on Einstein’s photoelectric equation.

The maximum kinetic energy of emitted photoelectrons is given by

K_{max} = E - \phi

where E is the energy of incident photons and \phi is the work function of the metal.

Given photon energy,

E = 4.2\ \text{eV}

Work function of the metal,

\phi = 2.2\ \text{eV}

So, maximum kinetic energy of photoelectrons is

K_{max} = 4.2 - 2.2 = 2.0\ \text{eV}

The stopping potential V_0 is defined by the relation

K_{max} = eV_0

Since kinetic energy is already in electron-volts, the numerical value of stopping potential in volts is the same.

Thus,

V_0 = 2\ \text{V}

Hence, the correct option is (2).