Question

Electrons accelerated from rest by a potential difference of $12.75V$, are bombarded on a mono-atomic hydrogen gas. Possible emission of spectral lines are:-

• A. First three Lyman lines, first two Balmer's lines and first Paschen line
• B. First three Lyman lines only
• C. First two Balmer's lines only
• D. None of the above.

Answer 1

The correct option is A First three Lyman lines, first two Balmer's lines and first Paschen line

$\begin{array}{c}\text{when it get energy of}12.75\text{ev it excited to}\\ n=4E_4-E_1=12.75ev\end{array}$

$\begin{array}{c}\text{then after it comes down, possible emission will}\\ \text{be}\end{array}$

$\begin{array}{c}\text{Line fall on}n=1\text{ane lyman line}=3\\ \text{Line fall on}n=2\text{are balmer line}=2\\ \text{Line fall on}n=3\text{are paschen line}=1\end{array}$