How many photons are produced in a laser pulse of 10 mW at 535 nm ?

The energy of one laser photon with wavelength of 535 nm is

 

1 W = 1 J/s, so that 10 mW is 0.01 J/s. Thus, the number of photons with an energy of 3.71 x 10^-19 J is

 

It means that a laser pulse of 10 mW of 535 nm generated 2.69x10^16 photons per second.