A photon has an energy of 
. Calculate the momentum of the photon.
A laser beam has a power of 
. The light from the laser has a wavelength of 
.
Determine the number of photons emitted by the laser in a time of 
.
The laser beam is incident normally on a surface that absorbs all of the photons. Show that the force 
exerted on the surface by the laser beam is given by
where 
is the power of the laser beam and 
is the speed of light.
.
.
