Question

Ionisation potential of hydrogen atom is 13.6 eV. Hydrogen atom in ground state is excited by monochromatic light of energy 12.1 eV. The spectral lines emitted by hydrogen according to Bohr?? theory will be

• A. one
• B. two
• C. three
• D. four

Answer 1

Answer: (C)

three

Answer 2

Since ionisation potential of hydrogen atom is 13.6 eV. $\therefore\quad E_{1} = -13.6 e V$ Now, $E_{n} - E_{1} = \frac{-13.6}{n^{2}}-\left(-13.6\right)=12.1$ $\frac{-13.6}{n^{2}}+13.6 = 12.1$ $\therefore\quad n = 3$ After absorbing 12.1 eV, the electron of H-atom is excited to 3 shell. Thus, possible transitions are 3 i.e., 3 $\to$ 2, 2 $\to$ 1 and 3 $\to$ 1