If the wavelength of green light is about 5000 Å , then the frequency of its wave is

$\mathrm{\lambda }=5000$Å

$\lambda =5000\times {10}^{-10} m$

$\mathrm{\lambda }=5\times {10}^{-7} \mathrm{m}$

$\mathrm{C}=3\times {10}^8 \mathrm{m}/\mathrm{s}$

$\mathrm{Frequency}\left(\mathrm{\vartheta }\right)=\frac{\mathrm{C}}{\mathrm{\lambda }}$

                         $=\frac{3\times {10}^8}{5\times {10}^{-7}}$

                       $\mathrm{\vartheta }=6\times {10}^{14} {\sec }^{-1}$.