The angular momentum of an electron in H-atom is \( \displaystyle\frac{3h}{2\pi} \), where \( h \) is Planck's constant. The kinetic energy of the electron is
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 1.51 eV
In the Bohr model the angular momentum is quantized, \( L = nh/2\pi \), so the given value fixes the orbit. In orbit n of hydrogen the kinetic energy is \( 13.6/n^{2} \) eV, equal to the magnitude of the total energy.
\( \displaystyle \frac{nh}{2\pi} = \frac{3h}{2\pi} \quad\Rightarrow\quad n = 3 \)
\( \displaystyle K = \frac{13.6\,\mathrm{eV}}{3^{2}} \approx 1.51\,\mathrm{eV} \)