Question
When a gun is fired at a distance, why is it that the flash is seen almost instantaneously while the sound is heard a little later?
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Answer
The reason is that the speed of light in air is $3 \times 10^8 ms^{-1}$ which is much larger as compared to the speed of sound in air $3 \times$ $10^2 ms^{-1}$. Hence light takes almost negligible time in comparison to sound in reaching us from the gun.
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