As a sound source moves away from a stationary observer, the number of waves will.
decrease
This question is very vague, and poorly written.
Thats all they have
A)increase
B)decrease
C)remain they same
D)need to know the speed of the source
To understand why the number of waves decreases as a sound source moves away from a stationary observer, we need to consider the concept of wavelength and frequency.
The wavelength of a sound wave refers to the distance between two consecutive points in the wave that are in phase (e.g., the distance between two peaks or two troughs). The frequency of a sound wave is the number of complete wavelengths that pass a point in a given period of time.
When a sound source moves away from a stationary observer, the distance between successive wavefronts (the peak or trough of each wave) increases. This means that the wavelength of the sound wave increases. In other words, the sound waves get stretched out.
However, the frequency of the sound wave remains constant. The frequency is determined by the source of the sound and does not change as the sound moves through space. For example, if the sound source emits 1000 waves per second, it will continue to emit 1000 waves per second regardless of its distance from the observer.
As a result, when the wavelength increases and the frequency stays the same, the number of waves that reach the observer per unit of time decreases. This is because it takes longer for each wave to reach the observer due to the increased distance between them. Therefore, as the sound source moves away from the observer, the number of waves received per second decreases, leading to a decrease in the perceived intensity or pitch of the sound.