Question

At the time when it is cloudy, there may be frequent thunder and lightning. The sound of thunder takes some time to reach you after you see lightning. Can you answer why this happens? Measure this time interval using a digital wrist watch or a stopwatch. Calculate the distance of the nearest point of lightning. (Speed of sound in air$=346m{{s}^{-1}}$).

Answer 1

Velocity of light is greater than the velocity of sound. So we see lightning faster than the time before the thunder is heard. Since the velocity of light is very much greater than that of the velocity of sound, that’s why we see lightning first. The value of velocity of light is $3\times {{10}^{8}}m/s$ and speed of sound in air is $346m{{s}^{-1}}$.

Formula used:
$\Rightarrow V=\dfrac{S}{t}$

Complete step by step answer:
Velocity of light is very much greater than that of the velocity of sound. So we see lightning faster than the time before the thunder is heard. Since the velocity of light is much greater than the velocity of sound, that’s why we see the lightning first. The value of velocity of light is $3\times {{10}^{8}}m/s$and speed of sound in air is $346m{{s}^{-1}}$. That is, the velocity of light is much greater than the velocity of sound. We can neglect the time interval between the lightning and the time we see them, because it is a negligible value.
Thus the distance of the nearest point of lightning is,
$\Rightarrow V=\dfrac{S}{t}$
By rearranging the equation we get,
$\Rightarrow S=Vt$
Hence by substituting the value of velocity and time,
Given that $V=346m{{s}^{-1}}$
$\therefore S=346\times t$
Thus, S = 346t m

Note:
The velocity of light is much greater than the velocity of sound. So we see lightning faster than the time before the thunder is heard. Since the velocity of light is much greater than the velocity of sound, that’s why we see the lightning first. Since the velocity of light is much greater than the velocity of sound, that’s why we see the lightning first.