College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 28

A laser used in eye surgery emits a 3.00-mJ pulse in 1.00 ns, focused to a spot 30.0 µ m in diameter on the retina. (a) Find (in SI units) the power per unit area at the retina. (This quantity is called the irradiance. ) (b) What energy is delivered per pulse to an area of molecular size (say, a circular area 0.600 nm in diameter)