Question

Find the second longest wavelengths (in $\mathring{A}$) emitted when hydrogen atoms make transitions and the spectral lines lie in the visible region(R = 1.097 $\times$ m${}^{-1}$).

Answer 1

As we know,
Longest $\lambda$ = Shortest energy gap
In visible region,
3 $\to$ 2
and
4$\to$ 2
are the two longest wavelengths
${\lambda }_{3\to 2}$ = $6562.8A^0$
${\lambda }_{4\to 2}$ = $4861.3A^0$
so these are the longest wavelengths.