Answer & explanation
Correct answer: option 2
for electron in an orbit $\frac{mv^2}{r} = \frac{ke^2}{r^2}$
$\Rightarrow mv^2 = \frac{ke^2}{r}$
$\Rightarrow K.E = \frac{1}{2}mv^2 = \frac{ke^2}{2r}$
Correct answer: option 2
for electron in an orbit $\frac{mv^2}{r} = \frac{ke^2}{r^2}$
$\Rightarrow mv^2 = \frac{ke^2}{r}$
$\Rightarrow K.E = \frac{1}{2}mv^2 = \frac{ke^2}{2r}$