Question

Let $E_n=\frac{-m{e}^2}{8{\epsilon }_0^2{n}^2{h}^2}$ be the energy of the $n^{th}$ level of $H$-atom. If all the $H$-atoms are in the ground state and radiation of frequency $(E_2-E_1)/h$ falls on it, then

• A. it will not be absorbed at all
• B. some of atoms will move to the first excited state
• C. all atoms will be excited to the $n=2$ state
• D. all atoms will make a transition to the $n=3$ state

Answer 1

Answer: (B)

The given energy of $n^{th}$ level of hydrogen atom is
$E_n=-\frac{m{e}^2}{8{\epsilon }_0^2{n}^2{h}^2}$
Since all the $H$-atom are in ground state $(n=1)$ then the radiation of given frequency $\frac{E_2-E_1}{h}$ falling on it may be absorbed by some of the atoms and move them to the first excited state $(n=2)$.