Question

It is estimated that a signal takes 1.27 seconds to reach the earth from the surface of the moon. Calculate the distance of the moon from the earth. Given speed of radio signal = 3$\times$ 10⁸ m/s (speed of light in air).

• A. 3.81 * 10⁸ km
• B. 3.81 * 10⁵ km
• C. 3.81 * 10⁵ m
• D. 3.81 * 10⁸ m

Answer 1

The correct option is (A) and (B)

3.81 $\times$ 10⁵ km

$3.81\times {10}^8$ m

Step 1, Given data

Speed = 3 $\times$ ${10}^8$ m/s

Time = 1.27 s

Step 2, Finding the distance traveled

We know,

Distance = speed $\times$ time

Putting all the values

Distance = 3 $\times$ ${10}^8$ m/s $\times$ 1.27 s = 3.81 $\times$ ${10}^8$ m = $3.81\times {10}^8$ m = 3.81 $\times$ ${10}^5$km

Hence the total distance traveled is $3.81\times {10}^8$ m and $3.81\times {10}^{5}km$ .