Question

Wavelength of $A = 400\text{ }nm$.

Wavelength of $B(\lambda) = \frac{C}{v} = \frac{3 \times 10^{8}}{10^{16}} = 3 \times 10^{- 8} = 30 \times 10^{- 9} = 30\text{ }nm$.

Wavelength of $C(\lambda) = \frac{1}{\bar{v}} = \frac{1}{10^{4}} = 10^{- 4}\text{ }cm = 10^{- 6}\text{ }m = 1000\text{ }nm$

Here $\lambda_{C} > \lambda_{A} > \lambda_{B}$

Energy $(E) \propto \frac{1}{\lambda}$

So $E_{B} > E_{A} > E_{C}$.