Answer :
Given:
The wavelength of the violet visible light is,
[tex]\begin{gathered} \lambda=420\text{ nm} \\ =420\times10^{-9}\text{ m} \end{gathered}[/tex]To find:
The frequency
Explanation:
The speed of the violet visible light in air is,
[tex]c=3\times10^8\text{ m/s}[/tex]The frequency is,
[tex]\begin{gathered} f=\frac{c}{\lambda} \\ =\frac{3\times10^8}{420\times10^{-9}} \\ =7.14\times10^{14}\text{ Hz} \end{gathered}[/tex]Hence, the frequency is
[tex]7.14\times10^{14}\text{ Hz}[/tex]