The speed of a photon is:
[tex]v=3.0\times10^8\text{ m/s}[/tex]The wavelength is given as:
[tex]\lambda=4.36\times10^4m[/tex]The relationship between speed, wavelength, and frequency is:
[tex]v=\lambda f[/tex]Substitute the values of v and λ, and solve for f
[tex]\begin{gathered} 3\times10^8=4.36\times10^4\times f \\ \\ f=\frac{3\times10^8}{4.36\times10^4} \\ \\ f=6880.7\text{ Hz} \end{gathered}[/tex][tex]f=6.88\times10^3Hz[/tex]