Question

The moon is $4\times {10}^{8}m$ away from the earth. A radar signal with a velocity of $3.08\times {10}^{8}m/s$ transmitted from the earth will reach the moon in about :

• A. 5.2s
• B. 1.3s
• C. 2.6s
• D. 0.70s

Answer 1

The correct option is B 1.3s

Distance between moon and earth, $S=4\times {10}^{8}m$

Speed of radar signal, $c=3.08\times {10}^{8}m/s$

We know,

Distance between moon and earth,

$S=c\times t$, where $t$ is the time taken by the radar signal to reach moon.

$\Rightarrow 4\times {10}^8=3.08\times {10}^8\times tor,t=\frac{4\times {10}^8}{3.08\times {10}^8}$

$t=1.3s$

Hence it will take 1.3 seconds for the radar signal to reach from earth to moon