Question

Light in a vacuum travels at a constant speed of 3x108 m/s. If the Moon's average distance from the Earth is 38324203 km, how long would it take for a beam of light to travel from the Earth, to the Moon, and back to the Earth again?

Answer 1

In this case we will use the next formula

$s=\frac{d}{t}$

where s is the speed, d is the distance and t is the time

In ur case

s= 3x10^8 m/s

we multiply by two the distance given because it is the double of the distance

d=2(38324203 )=76648406 km

and then we need to transform it into m

d=7.66x10^10m

Then we substitute

$3\times10^8=\frac{7.66\times10^{10}}{t}$

Then we isolate the t

$t=\frac{7.66\cdot10^{10}}{3\cdot10^8}=255.5s$

ANSWER

t=255.5 s