The width of the beam is determined by diffraction, caused by the finite aperture of the laser: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/cirapp.html h

The width of the beam is determined by diffraction, caused by the finite aperture of the laser: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/cirapp.html http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/cirapp.htm...