The energy E for an electron in H atom is $\large\frac{21.7\times 10^{-12}}{h^2}$erg.Calculate the energy required to remove electron completely from $n=2$ orbit.Also calculate the longest wavelength of light that can be used to cause this transition.

Question

$\begin{array}{1 1}(a)\;4367.4A^{\large\circ}&(b)\;3263A^{\large\circ}\\(c)\;3663.6A^{\large\circ}&(d)\;2348.1A^{\large\circ}\end{array}$