Question

Flash and thunder are produced simultaneously. But thunder is heard a few seconds after the flash is seen. Why?

Answer 1

Speed of sound in air $(330$ $m{s}^{-1})$ is very less than speed of light in air $(3\times {10}^{8}m/s)$.

Hence although flash and thunder are produced simultaneously, light (flash) reaches the earth surface a little earlier than sound (i.e thunder) .

So thunder is heard a few seconds after the flash is seen.