Question

Number of visible lines when an electron returns from $5^{th}$ orbit to $2^{nd}$ orbit in H-spectrum:

• A. 5
• B. 4
• C. 3
• D. 10

Answer 1

The correct option is C 3

Spectral lines corresponding to the visible frequencies/wavelength belong to the Balmer series. This happens when an electron falls from a higher energy level to the level corresponding to $n=2$.

When an electron transits from $n=5$ to $n=2$, there are 3 possible lines in visible region with transitions:
$2\leftarrow 5,2\leftarrow 4,and2\leftarrow 3$