Chapter 22, Problem 39GP

(a)

To determine

The time taken by a message to reach the moon sent from earth.

Answer to Problem 39GP

  $1.28s$

Explanation of Solution

Given info:

Distance between earth and moon, $d=3.84\times {10}^{8}m$

Speed of light, $c=3.00\times {10}^{8}m/s$

Formula used:

Time: $\Delta t=\frac{d}{c}$

Where,

  $\Delta t$ is time.

  $d$ is distance.

  $c$ is the speed of light.

Calculation:

Substitute the given values in formula, $\Delta t=\frac{d}{c}$

  $\Delta t=\frac{3.84\times {10}^{8}m}{3\times {10}^{8}m/s}=1.28s$

Conclusion:

Thus, the time taken by a message to reach the moon sent from earth is $1.28s$

(b)

To determine

The time taken by a message to reach mars sent from earth.

Answer to Problem 39GP

  $260s$

Explanation of Solution

Given info:

Distance between earth and mars, $d=78\times {10}^{6}km=78\times {10}^{9}m$

Speed of light, $c=3.00\times {10}^{8}m/s$

Formula used:

Time: $\Delta t=\frac{d}{c}$

Where,

  $\Delta t$ is time.

  $d$ is distance.

  $c$ is the speed of light.

Calculation:

Substitute the given values in formula, $\Delta t=\frac{d}{c}$

  $\Delta t=\frac{78\times {10}^{9}m}{3\times {10}^{8}m/s}=260s$

Conclusion:

Thus, the time taken by a message to reach mars sent from earth is $260s$ .