Ionization of energy of gaseous Na atoms is $\;495.5\;kJmol^{-1}\;$.The lowest possible frequency of light that ionizes a sodium atom is $\;(h=6.626 \times 10^{-34}\;Js\;N_{A}=6.022 \times 10^{23}\;mol^{-1})\;$

Question

$(a)\;7.50 \times 10^{4}\;s^{-1}\qquad(b)\;4.76 \times 10^{14}\;s^{-1}\qquad(c)\;3.15 \times 10^{15}\;s^{-1}\qquad(d)\;1.24 \times 10^{15}\;s^{-1}$