The momentum of light is exactly reversed when reflected straight back from a mirror, assuming negligible recoil of the mirror. thus the change in momentum is twice the photon momentum. suppose light of intensity 1.00 ~\text{kw/m}^21.00 kw/m 2 reflects from a mirror of area 2.00 ~\text{m}^22.00 m 2 . using the most general form of newton’s second law, what is the force on the mirror?

W= fd
where f is an applied force and d is the distance over which it is applied. when a parachuting skydiver is at constant velocity, he is experiencing "terminal velocity", the point at which his acceleration down is canceled out by air resistance. that means that the resisting force of the air is equal to his weight, but in the opposite direction. with this, we can solve for the work done by the force.
w = fd
w = (92.0)(9.81 m/s^2) (325)
w= 2.93 x 10^5 j
the value for work in this case is positive because it is pushing up on the skydiver, who has a downward force of gravity.
therefore the answer is 2.93 x 10^5 j

Sound wavelength of visible light waves