(a) According to Bohr’s theory of hydrogen atom , angular momentum is quantized $ie,$
$\ \ \ \ \ \ \ \ \ \ \ L\ = \ mv_{n}r_{n}\ = \ n\left( \frac{h}{2\pi} \right)$
Or L $\propto n$
Radius of the orbit $r_{n} \propto \frac{n^{2}}{Z}$
Kinetic Energy $= \frac{kZ^{2}e^{2}}{{2n}^{2}}$ $ie,$ $k$ $\propto \frac{1}{n^{2}}$