# Calculate the intensity

1. Jun 17, 2014

### ericwithakay

So I understand that to calculate the intensity a distance d away from a light-bulb you would treat the light-bulb as a point source and do a gaussian-sphere-type-of-thing to figure out the intensity at the desired location.

My problem involves a solid object made up of "point" light sources and I'm wondering whether I need integration to be able to solve the problem.

Any advice would be greatly appreciated.

Thanks

-E

2. Jun 17, 2014

### dimitri151

Yeah, sounds like you'll need to integrate. I think you could get this with a little more work.
You want your differential element of your body, be it area, volume, what have you, to have some measure of luminosity. So say you have the unit circle that has luminosity m per unit area. Then you subdivide your circle into little differential elements dA. Then for each dA the luminosity you observe at point (p,q) is (m/[(x-p)^2+(y-q)^2])dA lumens from each dA or whatever measure of light intensity you are using (that's the Guassian sphere thing you mentioned). That is, the luminosity falls according to the inverse square of the distance. If you integrate over the area of the circle you get the total luminosity an observer at (p,q) gets. Not an easy integral though.