The inverse square law dictates intensity, not energy, of light. In general usage, these are the same things, as more photons = more energy.<br /><br />When the inverse square law, or the intensity in general (as the 1/r^2 law holds <i>only</i> for spherical radiating objects) drops to levels akin to the individual energy levels of the photons, you begin to see light's particle nature.<br /><br />Instead of geting a steady energy reading from your instruments, it'll begin to become spotty, and as you turn down the intensity further, the problem will only get worse, as you'll only register any energy at all, whenever a photon hits it.<br /><br />I.e instead of getting 10,000 photons a second (bluring the signal out into a continous reading), you'll get 2 or three, and be able to register each individually. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>