Light of frequency is incident normally on a metal surface whose threshold frequency is

PHYSICS · Subjective · CBSE · Physics · Dual Nature of Radiation and Matter · Dual Nature of Radiation and Matter

Problem

Light of frequency

2\nu_0

is incident normally on a metal surface whose threshold frequency is

\nu_0

. With an incident intensity

I

, the stopping potential required to cut off the photocurrent is found to be

3\,\text{V}

. (i) Calculate the work function

\phi

of the metal in electron-volts. (ii) If the intensity of the incident light is increased to

3I

while the frequency is kept at

2\nu_0

, determine the new values of (1) the maximum kinetic energy of the emitted electrons and (2) the stopping potential. (iii) Keeping the intensity at

I

, the frequency of light is now reduced to

1.5\nu_0

. Find the new stopping potential required to bring the photocurrent to zero. Take Planck’s constant

h = 6.6\times10^{-34}\,\text{J\,s}

and charge of electron

e = 1.6\times10^{-19}\,\text{C}