Answer
(c) $1.28\times10^{-6}\,m$
Work Step by Step
$n_{i}=5$ and $n_{f}=3$
Recall that
$\frac{1}{\lambda}=\frac{2.18\times10^{-18}\,J}{hc}(\frac{1}{n_{f}^{2}}-\frac{1}{n_{i}^{2}})$ where
$h=6.626\times10^{-34}\,J\cdot s$ and $c=3.00\times10^{8}\,m/s$
Then,
$\frac{1}{\lambda}=\frac{2.18\times10^{-18}\,J}{(6.626\times10^{-34}\,J\cdot s)(3.00\times10^{8}\,m/s)}(\frac{1}{3^{2}}-\frac{1}{5^{2}})$
$=7.79868\times10^{5}\,m^{-1}$
$\lambda=\frac{1}{7.79868\times10^{5}\,m^{-1}}=1.28\times10^{-6}\,m$
