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

Energy, $\mathrm{E}=\frac{\mathrm{hc}}{\mathrm{\lambda }}=\frac{6.626\times {10}^{-34}\mathrm{Js}\times 3.0\times {10}^8{ \mathrm{ms}}^{-1}}{4000\times {10}^{-12} \mathrm{m}}$

                                                       $\left(1\mathrm{pm}={10}^{-12} \mathrm{m}\right)$

$=4.9695\times {10}^{-17} \mathrm{J}$

Number of photons, N$=\frac{1 \mathrm{J}}{4.9695\times {10}^{-17} \mathrm{J}}$

                               $=2.0122\times {10}^{16}\text{ photons }$