by pat » Fri Feb 27, 2004 5:33 pm
For all of the below, I'm assuming a dust-free universe that contains only my light source and my one-meter square panel.
Just want to add here that the dimming of light as the square of the radius is a consequence of the fact that a sphere's surface area increases with the square of its radius. Imagine you have some large, but finite, number of photons that you release all at once from a point. If you count the number of photons that hit a one-meter square panel placed one meter from the source, there are going to be a great number more than would hit that same panel placed three kilometers away. And, in fact, if you got far enough away, you may actually find spots that don't get any photons. There are only a finite number of them.
But, very few light sources emit all of their photons in one burst. So, even if you were very, very far away, you'd likely get a couple of photons every now and again.
Last edited by
pat on Fri Feb 27, 2004 8:09 pm, edited 1 time in total.