Also, remember that this is medium-wavelength IR at 1500nm, which is between two and three times the wavelength of visible at 400-700nm approximately. The energ

Also, remember that this is medium-wavelength IR at 1500nm, which is between two and three times the wavelength of visible at 400-700nm approximately. The energy in a photon is calculated as E = hf = hc/l where h is Planck's constant and c is the speed of light, while l is the wavelength. Notice how the energy decreases nice and linearly as the wavelength increases - this is good!