Q 12-12-037JEE MainJEE Main 2025 (29 Jan, Shift 2)Easy
The number of spectral lines emitted by atomic hydrogen that is in the $4^{\text{th}}$ energy level is
Answer: (C) $6$
From $n = 4$, electrons in a sample can drop by all possible routes. The number of distinct lines is
$$\frac{n(n-1)}{2} = \frac{4\times3}{2} = 6$$
($4\to3, 4\to2, 4\to1, 3\to2, 3\to1, 2\to1$).
Solution by Sreeraj P, M.Sc Physics