Q. The number of spectral lines that can be possible when electrons in 7th shell in different hydrogen atoms return to the 2nd shell, is
A) 12
B) 15
C) 14
D) 10
Explanation
(b)
Number of spectral lines $= \frac{\left( n_{2} - n_{1} \right)(n_{2} - n_{1} + 1)}{2}$
$= \frac{(7 - 2)(7 - 2 + 1)}{2} = 15$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.