you are standing on a street corner, and you hear a fire truck approaching. does the pitch of the siren stay constant, increase, or decrease as it approaches you? does the pitch of the siren stay constant, increase, or decrease as it moves away?
When a fire truck with a siren approaches you, the pitch of the siren will increase. This phenomenon is known as the Doppler Effect. The Doppler Effect occurs because the sound waves emitted by the siren are compressed as the fire truck moves closer to you, causing an increase in frequency or pitch. To understand how this works, consider the following steps:
1. As the fire truck moves towards you, it emits sound waves. These sound waves are initially spaced out at a particular frequency (pitch).
2. As the fire truck moves closer, each successive sound wave is compressed, meaning the waves get closer together.
3. Since frequency is the number of wave crests passing a fixed point in a given time, the closer proximity of the wave crests increases the frequency observed by an observer (you), resulting in a higher pitch.
Conversely, when a fire truck with a siren moves away from you, the pitch of the siren will decrease. In this case, the sound waves are stretched out as they move away, leading to a lower frequency or pitch. The same principles of the Doppler Effect apply; as the waves become more spaced out, the frequency observed by you decreases.
So, to summarize, as the fire truck approaches you, the pitch of the siren increases, and as it moves away, the pitch decreases.