Physics - Modern Physics Question with Solution | TestHub

For Balmer series, transition is from $n=3,4,5,6, etc$ to $n=2$.

For transition to $n=2$, the minimum state to transition from is $n=3$. 

Therefore, energy required $\Delta E=E_3-E_1=-\frac{13.6}{9}-\left(-13.6\right)=12.1\mathrm{eV}$