An observer detects an apparent frequency of 505 hz coming from a 500 hz source. Which is true?
a. the observer is moving due east, away from the stationary source
b. the source is moving due west, away from the stationary observer
c. the souce and the observer are moving away from eachother
d. the observer is moving toward the stationary source
e. a, b and c are possible
I think it's E.
You are wrong. Higher pitch they are moving closer.
thanks
To determine the correct answer, we need to apply the Doppler effect equation. The apparent frequency observed by the observer can be calculated using the equation:
f' = f * (v + vo) / (v + vs)
Where:
f' is the apparent frequency observed by the observer
f is the actual frequency emitted by the source
v is the speed of sound in air
vo is the velocity of the observer
vs is the velocity of the source
In this case, the apparent frequency observed is 505 Hz, and the actual frequency emitted by the source is 500 Hz.
Now, let's consider each option:
a. The observer is moving due east, away from the stationary source.
If the observer is moving away from the source, their velocity (vo) is positive. However, since the apparent frequency is higher than the actual frequency, the relative velocity between the observer and the source (v + vo) must be greater than the speed of sound (v). But since the observer is moving in the same direction as the sound waves, the relative velocity between them should be v - vo. Therefore, option a is NOT possible.
b. The source is moving due west, away from the stationary observer.
If the source is moving away from the observer, its velocity (vs) is positive. Similar to option a, the relative velocity between the observer and the source should be v - vs. Therefore, option b is NOT possible.
c. The source and the observer are moving away from each other.
If both the source and the observer are moving away from each other, both their velocities (vo and vs) are positive. The relative velocity between them would be (v + vo) + (v + vs) = 2v + vo + vs, which is greater than the speed of sound (v). Therefore, option c is a possible scenario.
d. The observer is moving toward the stationary source.
If the observer is moving towards the source, their velocity (vo) is negative. Similar to the previous cases, the relative velocity should be v - vo. Therefore, option d is NOT possible.
e. Options a, b, and c are possible.
As we have determined, options a and b are not possible. So, option e is NOT correct.
In conclusion, the correct answer is c. The source and the observer are moving away from each other.