Question

At a given point in its orbit, the moon is 2.4 x 10^5 miles from earth. How long does it take light from a source on earth to reach a reflector on the moon and then return to earth? (speed of light is 3.0 x 10^8 m/s)

Answer 1

Answer:

Total time= 2.56 s

Explanation:

Given that

$Distance = 2.4\times 10^5\ miles$

So distance = 386242560 m

Velocity of light

$C= 3\times 10^8\ m/s$

We know that

Distance = velocity x time

Now by putting then values

$time=\frac{386242560}{3\times 10^8}$

t=1.28 s

So the total time = 2 x 1.28

total time= 2.56 s

Answer 2

Explanation:

Given that,

Distance between moon and earth, $d=2.4\times 10^5\ miles$

1 mile = 1609.34 meters

$d=386241600\ m$

Speed of light, $c=3\times 10^8\ m/s$

We need to find the time taken by the light from a source on earth to reach a reflector on the moon and then return to earth. Time is given by :

$t=\dfrac{d}{c}$

$t=\dfrac{386241600\ m}{3\times 10^8\ m/s}$      

t = 1.28 seconds

Hence, this is the required solution.