Bohr Model Questions

Energy of an electron is given by $E=-2.178\times 10^{-18}\frac{Z^2}{n^2}\text{J}$. Wavelength of light required to excite an electron in a hydrogen atom from level $n=1$ to $n=2$ will be ($h=6.62\times 10^{-34}\text{Js}$ and $c=3.0\times 10^8{\text{ms}}^{-1}$):

In a hydrogen like atom electron makes transition from an energy level with quantum number $n$ to another with quantum number $(n-1)$. If $n\gg 1$, the frequency of radiation emitted is proportional to: