Which one of the following corresponds to the wavelength of line spectrum of H atom in its Balmer series ? ( $R=$ Rydberg constant)

The radius of third orbit of hydrogen atom is $R \mathrm{pm}$. The radius of second orbit of $\mathrm{He}^{+}$ion (in pm is)

The threshold frequency of a metal is $10^{15} \mathrm{~s}^{-1}$. The ratio of maximum kinetic energies of the photoelectrons, when the metal is made to strike with radiations of frequencies $1.5 \times 10^{15} \mathrm{~s}^{-1}$ and $2.0 \times 10^{15} \mathrm{~s}^{-1}$ respectively is