You stand 2.7 m from a 150 W light bulb that converts 5% of the electrical energy dissipated within it to light.
(a) If the pupil of your eye is 5 mm in diameter, how much energy enters you eye per second? ___J
The Attempt at a Solution
I thought, since the total power output is 150W * 5% = 7.5, I could fine the Pave by Pave=Ptotal ^2 x 0.5 = 28.125. That did not work. I don't understand why this approach would not equal the answer, knowing that Power=Energy/sec, and we're assuming 1 sec. here. Thank you.