Question

Th power of a red laser (wavelength of 630nm) is 450 watts. how many protons per second does the laser emit?

Answer 1

The energy of a single photon is E = h c/ λ

h=Planck's constant = 6.62 x10^-34 J.s

c=speed of light = 3x10^8m/s

λ =wavelength = 630 nm = 630 x10^-9 m

Then,

the energy of one photon E = h c/ λ

                                        = 6.62 x10^-34 Js* 3x10^8m/s / 630 x10^-9 m

                                        = 3.15 x10^-19 J

If the laser outputs 450 watt = 450 J/s,

then number of photons emitted = 450 J/s / 3.15x10^-19 J/photon

= 142.8 x10¹⁹ photon/sec