(adsbygoogle = window.adsbygoogle || []).push({}); 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/I_{0})

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*10^{11}* 0.01 = 6*10^{9}

A = 2π*200*1500 ~ 6π*10^{5}

I = (6*10^{9})/(6π*10^{5}) = (1/π)*10^{4}

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?

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# Homework Help: Sound intensity level of a thunder bolt

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