Force exerted on mirror by laser beam

[cantdophysics]

How much force (in Newtons) is exerted on a mirror when a 12.0W laser beam of red light (675 nm) strikes the mirror normal to its surface? (Assume no light is absorbed)

How how how how???
kthx

 

[Doc Al]

Hint: how would you solve the problem of a rubber bullet bouncing off a wall? Think Impulse = Force x Time = change in Momentum.

Does light have momentum?