It makes sense that lightening reaches us faster bcoz it travels at the speed of light while thunder travels at the speed of sound. But shouldn’t it last for same duration as thunder?
In: Physics
The light and sound waves travel many different paths to get to you, not just the most direct route. The light waves that don’t travel in the most direct route to you end up being dissipated to Be nearly undetectable to the human eye(unless they are hitting mirrors…), meanwhile the sound waves reach you after doing a bunch of reflections, meaning that the sound waves have travelled on a bunch of different paths of different distances, but of kept adequate intensity for you to hear. Because they have tracked different distances, they arrive at a bunch of different times.
The duration of the thunder is unrelated to the speed of the sound, it is the noise generated by the lightning vaporizing air particles in its way to the ground. The delay between seeing the lightning and hearing the thunder is due to the speed of light and sound, respectively, but the duration of the thunder is entirely dependent on the characteristics of the lightning, how long of a bolt it was, how much energy was in it, how many air particles it superheated on its way down, etc.
A few things are going on here.
First, different parts of the bolt are at different distances from you. Even if you had a theoretical bolt that was one straight line from cloud to ground, the portion hitting the ground is closer to you than the part in the cloud. The whole column of air gets superheated, making thunder. So you’ll hear the thunder generated by the closest part of the bolt to you first then hear it rumble along as the thunder from more distant parts of the bolt reach you. Now add in that most bolts change directions and fork, the resulting thunder will be heard with some variations depending on the distances of different parts of it.
Second, sound reflects. Sound bounces off hills, buildings, and just about anything else, essentially creating echoes that you hear even after the initial sound waves have reached you.
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