Question

In the hydrogen atom spectrum, the emission of the least energetic photon takes place during the transition from $n=6$ energy level to $n=$ _______ energy level.

• A. $1$
• B. $3$
• C. $5$
• D. $4$
• E. $2$

Answer 1

Answer: (C)

$5$

According to the relation
$\Delta E\propto \frac{1}{\lambda }\propto v\propto [\frac{1}{n_L^2}-\frac{1}{n_U^2}]$
In hydrogen atom the emission of the least energetic photon take place only when change in energy is minimum. This is possible for an electron that is present in $n=6$ and jumps to $n=5$.