(d) Given , $E_{n}\ = \ \frac{13.6}{n^{2}}\ eV$
Energy of photon ejected when electron jumps from $n$=3 state to $n$=2 state is given by
$\mathrm{\Delta}E = E_{3} - E_{2}$
$\therefore\ \ \ \ \ \ \ \ \ \ E_{3}\ = \ - \ \frac{13.6}{(3)^{2}}\ eV\ = - \ \frac{13.6}{9}\ eV$
$\ \ \ \ \ \ \ \ \ \ \ \ E_{2}\ = \ - \ \frac{13.6}{(2)^{2}}\ eV\ = - \ \frac{13.6}{4}\ eV$
So, $\ \ \ \ \ \mathrm{\Delta}E = E_{3} - E_{2}$ = $- \frac{13.6}{9} - \left( - \ \frac{13.6}{4} \right)$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = 1.9\ eV$ (approximately)