Frequency of the de-Broglie wave of election in
Bohr's first orbit of hydrogen atom is $\times 10^{13} \mathrm{~Hz}$ (nearest integer).
[Given : $\mathrm{R}_{\mathrm{H}}($ Rydberg constant $)=2.18 \times 10^{-18} \mathrm{~J} . h$ (Plank's constant) $=6.6 \times 10^{-34} \mathrm{~J} . \mathrm{s}$.]