Thank you for reporting, we will resolve it shortly
Q.
For a uniformly charged ring of radius $R$, the electric field on its axis has the largest magnitude at a distance $h$ from its centre. Then value of $h$ is :
Electric field on axis of ring
$E = \frac{kQh}{\left(h^{2}+R^{2}\right)^{3/2}} $
for maximum electric field
$\frac{dE}{dh} = 0 $
$ \Rightarrow h = \frac{R}{\sqrt{2}} $