Question

In a hydrogen atom, electron is in the $n^{th}$ excited state. It comes down to the first excited state by emitting $10$ different wavelengths. The value of $n^{th}$ is

• A. $6$
• B. $7$
• C. $8$
• D. $9$

Answer 1

Answer: (A)

$6$

Total no. of levels $=n-1$
$n\to 2$
Put $n^{\prime }=n-1$ in the formula attached
$\frac{(n-1)(n-2)}{2}=10$
$(n-1)(n-2)=20$
$\Rightarrow n=6$