posted by Koey on .
An owl has good night vision because its eyes can detect a light intensity as small as 5.0*10^-13 W/m^2. What is the minimum number of photons per second that an owl eye can detect if its pupil has a diameter of 8.5mm and the light has a wavelength of 510nm?
I really got no idea how to do it!!!PLEASE GUIDE ME STEP BY STEP!THANKS A LOT!!