Wavelength is the
ratio of speed of light and frequency:
wavelength = speed of
light / frequency
where frequency is: (c
is speed of light)
freq = c / wavelength = 3E8/550E-9 = 5.45E14 Hz
We know that photons have energy E = hf = 6.626E-34 Js * 5.45E14
Hz = 3.61 E-19 J
Therefore if it has 4.40 mJ of energy, the pulse has:
4.40E-3/3.61E-19 = 1.22E16 photons
