Q 12-12-019NEETJEE MainMedium
In a sample of hydrogen atoms excited to $n = 5$, the number of different spectral lines that can be emitted is
Answer: (D) $10$
$\dfrac{n(n - 1)}{2} = \dfrac{5 \times 4}{2} = 10$.
Solution by Sreeraj P, M.Sc Physics