Question

In a sample of H-atoms, if electrons make transition from $4^{th}$ excited state to $2^{nd}$ state then:

• A. 10 different spectral lines are observed
• B. 6 different spectral lines are observed
• C. Number of lines belonging to the Balmer series is 3
• D. Number of lines belonging to the Paschen series is 2

Answer 1

Answer: (B), (C), (D)

The correct options are
B 6 different spectral lines are observed
C Number of lines belonging to the Balmer series is 3
D Number of lines belonging to the Paschen series is 2


The $4^{th}$ excited state is the 5th energy state. So all possible transitions are $5\to 2,5\to 3,5\to 4,4\to 3,4\to 2,3\to 2$
So we have 6 different transitions and thus we will observe 6 different spectral lines.
Here the spectral lines which are observed when the electrons are coming back to the second energy state falls in the Balmer series. So the number of lines belonging to the Balmer series is 3.
The spectral lines which are observed when the electrons are coming back to the third energy state falls in the Paschen series. So the number of lines belonging to the Paschen series is 2.