Question

Find the two 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${}^{-1}$).

• A. 6562.8 $\mathring{A}$, 4861.3 $\mathring{A}$
• B. 6662.8 $\mathring{A}$, 4761.3 $\mathring{A}$
• C. 6762.8 $\mathring{A}$, 4661.3 $\mathring{A}$
• D. 6962.8 $\mathring{A}$, 4361.3 $\mathring{A}$

Answer 1

The correct option is A 6562.8 $\mathring{A}$, 4861.3 $\mathring{A}$

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