Chapter 25, Problem 51A

Whenever you watch a high-flying aircraft overhead, it seems that its sound comes from behind the craft rather than from where you see it. Why is this?

To determine

To explain: The reason for the given situation.

Explanation of Solution

Introduction:

Speed of light is much greater than the speed of sound in air.

When a person watches a high-flying aircraft moving overhead but hears the sound coming from far behind its current visual position because the light coming after reflecting from the airplane reaches his eyes too quickly compared to the sound it produces. The speed of sound in air is much lesser as compared to the sound of light. That is why, when the sound produced and light reflected at the same moment goes away from the aircraft, and then light reaches the observer’s eye within a fraction of a second. But, when the observer hears the sound of high-flying aircraft, the aircraft has already covered some distance ahead.

Conclusion:

Thus, the observer hears the sound of aircraft too late as compared to its actual position when the sound is produced because of the difference in the speed of light and sound waves.