Calculate the frequency in $\mathrm{H}_{\mathrm{z}}$ of orange colour light having wave length $600 \mathrm{~nm} .\left[\mathrm{C}=3 \times 10^8 \mathrm{~ms}^{-1}\right]$

The frequency of light is determined from the relationship $c = \lambda \nu$, where $c = 3 \times 10^{8} \text{ m/s}$ and $\lambda = 600 \text{ nm}$.

Convert the wavelength to meters: $\lambda = 600 \times 10^{-9} \text{ m} = 6 \times 10^{-7} \text{ m}$.

Rearranging the equation gives $\nu = \frac{c}{\lambda} = \frac{3 \times 10^{8}}{6 \times 10^{-7}} = \frac{1}{2} \times 10^{15} = 5 \times 10^{14} \text{ Hz}$.

This result corresponds to option B.