Light intensity at a distance

1. Aug 25, 2011

mdd16

Hello,

I need to calculate intensity of light at a distance of 24 inch from a tubular light source with a light intensity rating specified at 3.6 microwatts/sq.cm. per inch of lamp.

The light is a UV light which is to illuminating a cooling coil in air conditioning system. Supposedly there are germs on the surface of cooling coil which needs to be killed. There is a specified level of microwatts.seconds of UV dosage required to kill germs. (For this example we can assume it to be 4500). I want to calculate how long will it take to kill this germ.

Idea is to calculate incident intensity on target surface and then divide required dosage by incident intensity to get answer in seconds.

Can anyone help.

Thanks and regards
Mohan Dhingra