Sound travels at speed v=343 m/s, therefore the time the sound takes to cover a distance of
[tex]S= 1 cm=0.01 m[/tex]
is
[tex]t= \frac{S}{v}= \frac{0.01 m}{343 m/s}=2.9 \cdot 10^{-5} s [/tex]
Light travels at speed [tex]c=3 \cdot 10^8 m/s[/tex], therefore the distance it travels during the same time t is
[tex]S=ct=(3 \cdot 10^8 m/s)(2.9 \cdot 10^{-5} s)=8746 m=8.75 km[/tex]
