Question

A gas of monoatomic hydrogen is bombarded with a stream of electrons that have been accelerated from rest through potential difference of $12.75V$. In the emission spectrum, one can observe lines of

• A. Lyman series
• B. Balmer series
• C. Paschen series
• D. Pfund series

Answer 1

Answer: (A), (B), (C)

The correct options are
A Lyman series
B Balmer series
C Paschen series

The highest state that can be achieved the the electron is:
Energy attained $=Ve$
$E=12.75eV$
$12.75=13.6(1-\frac{1}{n^2})$
$1-\frac{1}{n^2}=\frac{15}{16}$

$\Rightarrow n=4$
So, the electron gets excited to $n=4$.
It can come back to $n=3$, $n=2$, $n=1$
Paschen, Blamer, and Lymen series