Question

15.25 you stand at X=o m listening to a sound that is emitted at frequency Fs. The figure shows the frequency you hear during a four-second of the following describes the motion of the second source?

A it moves from left to right and passes you at t=2s B it moves from right to left and passes you at t=2s C it moves toward you but doesn't reach you. It then reverses direction at t=2s
D it moves away from you until t=2s it then reverses direction and moves toward you, but doesn't reach you.

Answer 1

The correct description of the motion of the sound source is option D: it moves away from the observer until t=2s; it then reverses and moves toward the observer but doesn't reach them. This is based on the expected changes in frequency due to the Doppler Effect when a source first approaches and then moves away from the observer.

Step-by-step explanation:

Understanding the Doppler Effect in Sound Waves:

When considering the frequency of sound that an observer hears as related to a moving source, we utilize the principles of the Doppler Effect. If the source of the sound is moving towards the observer, the observed frequency increases; if the source is moving away, the observed frequency decreases. In the context of the provided information, when the source passes the observer at t=2s, we must consider the change in frequency observed over the four-second period to determine the motion of the source.

Without the figure provided, we can nonetheless deduce the motion based on the descriptions. If the frequency increases up to t=2s and then decreases, it suggests the source was moving toward the observer and then started moving away. Therefore, the correct option is D: it moves away from you until t=2s; it then reverses direction and moves toward you, but doesn't reach you, as this pattern matches the expected change in observed frequency when a source first approaches and then recedes from the observer's position.

The formula λs = vTs and λo = vTo helps us to understand how the wavelength and frequency change with motion of the source or observer relative to one another. These concepts are foundational in understanding how motion affects sound perception, a phenomenon widely studied in the field of acoustics and with applications in various technologies such as radar and medical imaging.