posted by Bill on .
Intensity of the HeNe laser (lambda = 632nm) was measured at 2 distances: 1m and 200m from the laser. The meter reading was 10W and 1W correspondingly. How many photons/sec will enter your eye if you look into the laser from 1m? From 2m? Assume that radius of the pupil was 2.4mm, radius of the detector was 3.5mm. At a distance of 1m the laser beam radius was 1mm.