A sound of constant frequency is produced by the si-ren on top of a firehouse. Compared to the frequen-cy produced by the siren, what is the frequency heard by a firefighter approaching the firehouse? What if the firefighter is driving away?
Driving toward, the frequency increases.
Driving away, the frequency decreases
When a sound source is stationary, like the siren on top of a firehouse, the frequency of the sound waves it produces remains constant. However, when an observer is in motion relative to the sound source, the observed frequency of the sound can be different.
For a firefighter approaching the firehouse:
- As the firefighter moves towards the firehouse, the sound waves produced by the siren are compressed, resulting in an increased frequency of the sound heard by the firefighter.
For a firefighter driving away from the firehouse:
- As the firefighter moves away from the firehouse, the sound waves produced by the siren are stretched out, resulting in a decreased frequency of the sound heard by the firefighter.
This phenomenon is known as the Doppler effect. The exact change in frequency depends on the relative speeds of the observer and the source, as well as the speed of sound in the medium through which the sound is traveling.
To understand the frequency heard by the firefighter approaching or driving away from the firehouse, we need to consider the concept of the Doppler effect.
The Doppler effect is the change in frequency or pitch of a sound wave due to the relative motion between the source of the sound wave and the observer. In this case, the sound wave is produced by the siren on top of the firehouse, and the observer is the firefighter.
When the firefighter is approaching the firehouse:
1. The frequency heard by the firefighter will be higher than the frequency produced by the siren.
This is because the sound waves are compressed as the firefighter moves towards the source. The closer the firefighter gets to the siren, the higher the frequency of the sound waves. This increase in frequency results in a higher pitch or tone of the sound.
When the firefighter is driving away from the firehouse:
1. The frequency heard by the firefighter will be lower than the frequency produced by the siren.
This is because the sound waves are stretched out as the firefighter moves away from the source. The farther the firefighter gets from the siren, the lower the frequency of the sound waves. This decrease in frequency results in a lower pitch or tone of the sound.
It's worth noting that the actual change in frequency depends on the relative speed between the observer and the source of the sound, as well as the speed of sound in the medium.