A laser produces a 4.80-mW beam of light, consisting of photons with a wavelength of 677.1 nm.

Question:

A laser produces a 4.80-mW beam of light, consisting of photons with a wavelength of 677.1 nm.
(a) How many photons are emitted by the laser each second? photons/s
(b) The laser beam strikes a black surface and is absorbed. What is the change in the momentum of each photon that is absorbed? kg m/s
(c) What force does the laser beam exert on the black surface? N