Question

Flash on thunder are produced simulant endlessly but thunder is heard a few seconds after the flash is seen why

Answer 1

The answer lies in the fact that the speed of light is
$3 \times 10 {}^{8} metres \: per \: second$
and the speed of sound is 343 m/s that's why the sound takes more time to propagate as compared to light.This is the reason that thunder is heard a few seconds after the flash is seen.

Answer 2

→The speed of sound is 344 m/s whereas the speed of light is 3 × 108 m/s. The speed of light is less when compared to that of light. Due to this reason, the thunder takes more time to reach the Earth as compared to the light speed which is faster. Hence, lightning is seen before whenever we hear the thunder.