Question

How far does light travel in the time it takes sound to travel 1 cm in air at 20°c?

Answer 1

The speed of sound at $20^{\circ}C$ is approximately v=343 m/s. The distance covered by the sound wave is
$s=1 cm=0.01 m$
And the time it takes is
$t= \frac{S}{v}= \frac{0.01 m}{343 m/s}=2.9 \cdot 10^{-5} s$

Now we want to find how far the light travels during this time. Light travels at speed $c=3 \cdot 10^8 m/s$, therefore the distance it covers during this time is
$S=ct = (3 \cdot 10^8 m/s)(2.9 \cdot 10^{-5} s)=8700 m$