During lightning ,both light and sound is produced . I want to know why light and sound is produced?
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2$\begingroup$ See: Why does lightning cause sound? $\endgroup$– John RennieJan 3, 2018 at 6:51
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2$\begingroup$ And: Why does lightning emit light? $\endgroup$– John RennieJan 3, 2018 at 6:52
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1 Answer
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Thunder is caused by lightning, which is essentially a stream of electrons flowing between or within clouds, or between a cloud and the ground. The air surrounding the electron stream is heated to as hot as 50,000 degrees Farhenheit, which is three times hotter than the surface of the sun. As the superheated air cools it produces a resonating tube of partial vacuum surrounding the lightning's path. The nearby air rapidly expands and contracts. This causes the column to vibrate like a tubular drum head and produces a tremendous crack. As the vibrations gradually die out, the sound echoes and reverberates, generating the rumbling we call thunder. We can hear the thundering booms 10 miles or more distant from the lightning that caused it.
When the lightning is within sight, however, we see it first because the speed of sound in air is considerably slower that that of the electron flow. Thus, the sound behaves more like a shock wave than an ordinary sound wave. The shock wave follows the path of the electrons like a fist in a sock. The speed of sound is even more insignificant when compared to the speed of light. The light from the flash reaches us in a fraction of a second, whereas the sound lags along like a snail following an interplanetary rocket.
The audiovisual spectacle of thunder and lightning is a combination of the dynamics of the vibration of air molecules and their disturbance by electrical forces.
answered Jan 3, 2018 at 6:22
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1$\begingroup$ The lightning channel is not a resonance tube. No reason to talk about tubular drum heads. $\endgroup$– user137289Jan 3, 2018 at 10:36
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$\begingroup$ @Pieter therefore your comment apply to the A by W Basu? For the part concerning the speed of charges flow compared to speed of sound... I thought it is reasonable that the arc creates a sonic boom $\endgroup$ Jan 3, 2018 at 10:53
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1$\begingroup$ @Alchimista But this is not like the sonic boom that accompanies supersonic airplanes. The expansion is produced along the length of the lightning channel at essentially the same instant. $\endgroup$– user137289Jan 3, 2018 at 11:43
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$\begingroup$ @Pieter. Yes. I think a sonic boom depart from each point of the arc giving a crack. Then we hear the returning air . Right? $\endgroup$ Jan 3, 2018 at 11:51