Wavelength of the emitted radiation $=616 \mathrm{~nm}=616 \times 10^{-9} \mathrm{~m}$ (Given)
(a)Frequency of the emission $(\nu)$
$
\nu=\frac{c}{\lambda}
$
Where, $c=$ speed of the radiation
$\lambda=$ wavelength of the radiation
Substituting these values in the expression for $(\nu)$ :
$
\nu=\frac{3 \times 10^{8} \mathrm{~m} / \mathrm{s}}{616 \times 10^{-9} \mathrm{~m}}

$$
=4.87 \times 10^{8} \times 10^{9} \times 10^{-3} s^{-1} v
$
$
=4.87 \times 10^{14} s^{-1}
$
Frequency of the emission $(\nu)=4.87 \times 10^{14} s^{-1}$