That's correct, intensity will decrease lesser than an isotropic source thus it will not fit into inverse square law. I was trying to draw a bigger picture but my expression was wrong. A LD cutting aliminium from 1cm will not cut the same material with the same applied power from 2cm. It all ends up at beam focus where you need to tighten your beam diameter thus intensity. On Thu, Jun 23, 2011 at 4:51 PM, Carey Fisher wr= ote: > On Thu, Jun 23, 2011 at 9:31 AM, Michael Watterson wro= te: > >> On 23/06/2011 13:15, Yigit Turgut wrote: >> > Intensity of light is reduced by inversely proportional to >> > square of the distance. >> not true with a laser. That would imply the spot doubles in diameter >> with double distance. many don't >> -- >> >> >> The Inverse Square Law only applies to a point (or equivalent) source > radiating energy in "all" directions - "all" directions meaning a spheric= al > surface subtending an angle of 4pi steradians. > Carey > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .