A laser emits a light pulse of duration = 0.13 ms and energy E = 10 J.

A laser emits a light pulse of duration τ = 0.13 ms and energy E = 10 J. Find the mean pressure exerted by such a light pulse when it is focused into a spot of diameter d = 10μm on a surface perpendicular to the beam and possessing a reflection coefficient p = 0.50.