Question

In biophysics experiments it is common to attach molecules to small plastic spheres with 500 nm radii (r = 5.0 ∗ 10−7m), and then use radiation pressure from a focused laser beam to push or pull on the spheres. If I want to produce a force of 10 picoNewtons (10−11N), and my laser is producing 60 milliWatts of power, what should the radius of the focused laser beam be?

Answer 1