Question

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

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

Answer 1

Answer: (B)

1.0 eV

Answer 2

According to Einstein's photoelectric equation.
The kinetic energy of emitted photoelectrons is
$K=h\nu-\phi_{0}$
where $h\nu$ is the energy of incident radiation and
$\phi_0$ is work function of the metal.
As per question,
0.5 eV=hv- \phi_0 \hspace15mm ...(i)
0.8 eV=1.2hv- \phi_0 \hspace15mm ...(ii)
On solving eqns. (i) and (ii), we get
$\phi_{0}=1.0 \,eV$