When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. The work function of the metal is:

Options

A. 1.3 eV
B. 1.5 eV
C. 0.65 eV
D. 1.0 eV

Answer

D

Explanation

`K_("max") = hv - phi_0`
`implies 0.5 = hv -phi = E -phi`
`implies E = 0.5 +phi " "...(i)`
And `0.8 = 1.2hv -phi = 1.2E -phi`
`implies E = (0.8 +phi)/(1.2) " "...(ii)`
From (i) and (ii) equation
`phi = 1eV`