The correct answer to your question and how to solve it is
The relation between wavelength (λ)and the frequency of electromagnetic oscillation (f) is described by the following expression: λ=c/f, where c–is the speed of light in vacuum = 3*10^8 m/s Derive f from above: f = c/λ.How to Calculate: λ=890nm = 890*10^-9m = 8.9*10^-7m f =3*10^8m/s Divided by 8.9*10^-7m = 0.34*10^15 s-1=3.4*10^14 s-1 So your Answer is: The frequency of radiation of wavelength 890 nm is 3.4*10^14s-1
The atomic number is the number of protons. So, you can subtract the atomic number from the mass number to find the number of neutrons. I hope this helps! :)
