\(E_{n}=-\frac{13.6}{n^{2}} \mathrm{eV}\)
\(\therefore E_{1}=-13.6 \mathrm{eV} ; E_{2}=-\frac{13.6}{2^{2}}=-3.4 \mathrm{eV}\)
\(E_{3}=-\frac{13.6}{3^{2}}=-1.5 \mathrm{eV} ; E_{4}=-\frac{13.6}{4^{2}}=-0.85 \mathrm{eV}\)
\(\therefore E_{3}-E_{2}=-1.5-(-3.4)=1.9 \mathrm{eV}\)
\(E_{4}-E_{3}=-0.85-(-1.5)=0.65 \mathrm{eV}\)