Chapter 26, Problem 26A

In the stands of a racetrack, you notice smoke from the starter’s gun before you hear it fire. Explain.

To determine

To Explain:Smoke is seen from the starter’s gun before one hears it.

Explanation of Solution

Introduction:

Light is a transverse wave, which has a speed nearly $3\times {10}^8\text{m/s}$ . Sound is a longitudinal wave with velocity $340\text{ m/s}$ in the air at room temperature.

Since the speed of light is much more than that of sound, the smoke from the gunfireis visible before the sound is heard. Therefore, one can see the light before one can hear its sound.

Conclusion:

Since light travels faster than sound, one can see the smoke from the gun before hearing the gunfire.