Question

Let $E_{n} = \frac{-me^{2}}{8\varepsilon_{0}^{2} n^{2}h^{2}}$ 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
$E_{n} =- \frac{me^{2}}{8\varepsilon_{0}^{2} n^{2}h^{2}}$
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 $(n = 2)$.