Dear forum members, I would like to ask some help regarding irradiance calculation. I am a high school student doing a project in biology in which I expose drosophila m. (fruit flies) to UVA radiation and I would like to mention in my paper the actual dose that was used. I know that... UV dose (J/m^2) = W/m^2 x s W/m^2 refers to irradiance, this is the formula that I found for calculating it: E= dΦ / d Ad 1. Ad is the area which is exposed to the radiation. What does the d in front of Ad stand for? dΦ = E0 cosθ d Ad So, the formula above is the radiation intensity (W)... 2. E0 is the irradiance of light incident upon material, how do I calculate that? From here I found the information: http://metrology.hut.fi/courses/S-108.4110/2007/RADIOMETRIA.pdf (on the 5th page) Lamp: Original Philips UVA Type HP3147/A 220V ~ 50 Hz 75W Thank you for any advice and help!