We will have the following:
First, we recall that:
[tex]\lambda=\frac{v}{f}[/tex]Then, we recall that the speed of light is 299 792 458 m/s; then:
[tex]\begin{gathered} \lambda=\frac{299792458m/s}{4.2\ast10^{14}Hz}\Rightarrow\lambda=7.137915667\ast10^{-7}m \\ \\ \Rightarrow\lambda\approx7.1\ast10^{-7}m \end{gathered}[/tex]So, the wavelength is approximately 7.1E-7 m.
