1. The problem statement, all variables and given/known data Find the sound intensity level of a thunder bolt, if a person is standing 200 m from the spot it hits. The bolt hits the ground vertically and the height of the bolt is 1500 m. The bolt has an electrical current of 20 kA and a voltage of 30 MV. It discharges thrice, each time lasts about 0.1 ms and the time between each discharge is about 30 ms. A reasonable approximation is that the sound wave equals 1% of the thunder bolt's energy. 2. Relevant equations P = UI A = 4πrh (supposedly the sound wave from the bolt expands in the shape of a cylinder) L = 10lg(I/I0) I = P/A 3. The attempt at a solution At first it seemed simple, I thought I got the right answer but I've been trying with everything... still getting the wrong answer. P = 6*1011 * 0.01 = 6*109 A = 2π*200*1500 ~ 6π*105 I = (6*109)/(6π*105) = (1/π)*104 Now I'm not entirely sure what to do. I thought that maybe, intensity can be written as I = P/At. Then I would just divide my intensity by the time the bolt lasts. Which is (0.3+60)*10(-3). I also thought that maybe I could just multiply my intensity by three since it happens so fast anyway. In either case I get the wrong answer after calculating the intensity level. Any ideas?