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Inertigratus
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Homework Statement
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.
Homework 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
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?