Question

A train makes an emergency stop and the train operator locates and corrects the problem. After the train recharges, the train operator's indication illuminates. What signal must the train operator receive from the conductor before starting the train?

Answer 1

The question deals with the Doppler effect, which causes higher observed frequencies as a train approaches a stationary observer and lower frequencies after it passes. The train's engineer observes a constant frequency.

Step-by-step explanation:

The student is asking about the Doppler effect in regard to a scenario involving a moving train. The Doppler effect explains how different frequencies are observed when the source of a wave is moving relative to an observer.

Answer Details:

1. Frequencies observed by a stationary person as the train approaches will be higher than when it passes because the sound waves are compressed as the train moves towards the observer.
2. After the train passes, the frequencies will be lower for the stationary person because the sound waves are elongated.
3. The frequency observed by the train's engineer remains constant since the engineer is moving with the source of the sound.

This phenomenon occurs because of the relative motion between the source of the sound (the train) and the observer (either the stationary person or the engineer).