Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state…
Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material. The stopping potential is measured to be $3.57 \mathrm{~V}$. The threshold frequency of the material is
$4 \times 10^{15} \mathrm{~Hz}$
$5 \times 10^{15} \mathrm{~Hz}$
$1.6 \times 10^{15} \mathrm{~Hz}$
$2.5 \times 10^{15} \mathrm{~Hz}$
Solution
Energy released from emission of electron
$\begin{aligned}
E & =(-3.4)-(-13.6) \\
& =10.2 \mathrm{eV}
\end{aligned}$
From photo electric equation.
Work function
$\begin{aligned}
\phi & =E-e V=h v \\
v & =\frac{E-e V}{h} \\
& =\frac{(10.2-3.57) e}{6.67 \times 10^{-34}} \\
v & =\frac{6.63 \times 1.6 \times 10^{-19}}{6.67 \times 10^{-34}} \\
& =1.6 \times 10^{15} \mathrm{~Hz}
\end{aligned}$