Question

The maximum kinetic energy of photoelectrons emitted from a metal surface increases from $0.4eV$ to $1.2eV$ when the frequency of the incident radiations increased by $40\%$. What is the work function (in $eV$ ) of the metal surface?

Answer 1

Answer: 1.6

According to Einstein's photoelectric equation,
$K_{\max }=hv-{\varphi }_0$
Where $K_{\max }$ is the maximum kinetic energy of photoelectrons and ${\varphi }_0$ is the work function of the metal surface
Initially,
hv $=0.4+{\varphi }_0$
When the frequency is increased by $40\%$, then
$1.4hv=1.2+{\varphi }_0$
On solving we get
${\varphi }_0=1.6eV$