# Find the wave length of radiation required to excite the electron in ground level of $Li^{++}(z=3)$ to third energy level.Also find the ionization energy of $Li^{2+}$.(R=$1.097\times 10^7m^{-1})$
$\begin{array}{1 1}(a)\;2.5\times 10^{-19}J&(b)\;1.95\times 10^{-17}J\\(c)\;2.5\times 10^{-17}J&(d)\;1.95\times 10^{-19}J\end{array}$