What is the number of photons of light with a wavelength of 4000 pm that provide 1 J of energy?

Energy of one photon, E=hcλ=6.626×10−34Js×3.0×108ms−14000×10−12m (1pm=10−12m) =4.9695×10−17J Number of photons, N=1J4.9695×10−17J=2.0122×1016 photons .