The kinetic energy of the electron in an orbit of radius r in hydrogen atom is (e = electronic charge)
Answer & explanation
Correct answer: option 2
Potential energy of electron in $n^{\text {th}}$ orbit of radius r in H-atom $U=-\frac{e^2}{r}$ (in CGS)
∵ K.E. = $\frac{1}{2}|P . E .| \Rightarrow K=\frac{e^2}{2 r}$