Question

A hydrogen atom in the ground state is excited by radiations of wavelength 975 A${}^o$. how many lines will be possible in absorption spectrum

• A. 2
• B. 3
• C. 4
• D. 5

Answer 1

Answer: (B)

3

Given : $\lambda =975$ $A^o=97.5$ nm

Energy of incident radiation $E=\frac{hc}{\lambda }=\frac{1242.4}{97.5}=12.74$ eV

Energy of the state into which the electron jumps $E=-13.6-(-12.74)=-0.85$ eV

We get $-0.86=\frac{-13.6}{n^2}$ $⟹n=4$

Hence the electron jumps from ground state upto $n=4$ state via transition from $1\to 2$, $1\to 3$ or $1\to 4$

Thus 3 lines are possible in absorption spectrum.