Practice MCAT Question - Q4 - Answer!
The frequency heard by a detector is higher than the frequency emitted by the source. Which of the statements below must be true?
A. The source must be moving away from the detector.
B. The source must be moving toward the detector.
C. The source and the detector may be moving toward each other.
D. The detector may be moving away from the source.
The correct answer is (C). This is the Doppler effect. Since the frequency is shifted to a higher value, the source and the detector must be getting closer together. This eliminated choices (B) and (D). Choice (A) is eliminated because it is not mandatory that the source be the device moving. The same effect is accomplished by holding the source steady and moving the detector toward it.
