The energy of a photon is `E=hf` , where f is the frequency of radiation and h is the Plank constant `h = 4.1 * 10^(-15) eV*s`
The frequency and the wavelength `lambda` are connected by the relationship
`f = c/lambda` , where c is the speed of light `c=3*10^8 m/s`
So, `E = (hc)/(lambda)` and `lambda = (hc)/E = (4.1*10^-15 * 3* 10^8 m)/2` = `6.1*10^-7 m = 600 nm`
The wavelength of a 2 eV photon is 600 nanometers.