Which situations might cause two observers (A and B) to measure different frequencies for the same
vibrating object? Select the two correct answers. (2 points)
Observer A and Observer B are moving at different speeds relative to each other.
Observer A is stationary and Observer B is moving.
Observer A and Observer B are both stationary and at the same distance from the object.
Observer A and Observer B are stationary but at different distances from the vibrating object.
Observer A and Observer B are moving at different speeds relative to each other.
Observer A and Observer B are stationary but at different distances from the vibrating object.
The correct answers are:
1. Observer A and Observer B are moving at different speeds relative to each other.
2. Observer A and Observer B are stationary but at different distances from the vibrating object.
In both of these situations, the relative motion between the observers and the vibrating object affects the frequencies they measure. The Doppler effect causes the frequency of a wave to change when there is relative motion between the source of the wave and the observer. Therefore, the motion of Observer A and Observer B can cause a difference in the frequencies they measure.
The correct answers are:
1. Observer A and Observer B are moving at different speeds relative to each other.
2. Observer A and Observer B are stationary but at different distances from the vibrating object.
To understand why these situations can cause two observers to measure different frequencies for the same vibrating object, let's explore the concept of Doppler effect.
1. Observer A and Observer B are moving at different speeds relative to each other:
When an object is in motion, the frequency of the sound waves it emits can be shifted for observers who are moving relative to the source. This phenomenon is known as the Doppler effect. If Observer A and Observer B are moving at different speeds relative to each other, they will experience different Doppler shifts, resulting in different frequencies being measured.
2. Observer A and Observer B are stationary but at different distances from the vibrating object:
The intensity and frequency of sound waves decrease with increasing distance from the source. When Observer A and Observer B are at different distances from the vibrating object, they will perceive the sound waves with different intensities and frequencies due to the inverse square law. This leads to a difference in the measured frequencies by the observers.
It's worth noting that when Observer A and Observer B are both stationary and at the same distance from the object, and when Observer A is stationary and Observer B is moving, the frequencies measured by both observers will be the same since there are no changes in relative speed or distance affecting the measurements.