Difficulty: Medium

Average Score: 67%

Have you ever wondered why the whistle of a traveling, distant locomotive predicts its approach several yards before anyone actually sees it? Or why an oncoming ambulance's screaming siren is heard momentarily several feet before the ambulance comes into full view, before it passes you, and why its siren is still heard faintly well after the ambulance is out of sight?
What you are witnessing is a scientific phenomenon known as the Doppler Effect. What takes place is truly remarkable. In both of these instances, when the train or ambulance moves toward the sound waves in front of it, the sound waves are pulled closer together and have a higher frequency. In either instance, the listener positioned in front of the moving object hears a higher pitch. The ambulance and locomotive are progressively moving away from the sound waves behind them, causing the waves to be farther apart and to have a lower frequency. These fast-approaching modes of transportation distance themselves past the listener, who hears a lower pitch.

Which statement is not listed as a detail in the passage?

Rationale

The oncoming sound waves have a higher pitch because of low frequency and closeness of waves.

The passage explains that sound waves in front of a moving object, like a train or ambulance, are compressed, leading to a higher frequency and thus a higher pitch. Therefore, stating that higher pitch results from low frequency contradicts the passage’s explanation.

A (The oncoming sound waves have a higher pitch because of high frequency and closeness of waves.) YOUR ANSWER

This statement accurately reflects the details in the passage. It describes the Doppler Effect, where sound waves compress in front of a moving object, increasing their frequency and resulting in a higher pitch for the listener.

B (The oncoming sound waves have a higher pitch because of low frequency and closeness of waves.) CORRECT

This statement is incorrect according to the passage. It mistakenly attributes higher pitch to low frequency, whereas the passage makes it clear that higher pitch is due to high frequency, caused by sound wave compression.

C (The whistling sound of the locomotive as it approaches and passes can be explained by the Doppler effect.) YOUR ANSWER

The passage explicitly mentions that the Doppler Effect explains the changing pitch of a locomotive's whistle as it approaches and then moves away, consistent with the details provided.

D (The high-pitched sound of the ambulance as it approaches and passes can be explained by the Doppler effect.) YOUR ANSWER

This statement is also consistent with the passage. The Doppler Effect is used to describe the change in pitch of an ambulance's siren as it moves toward and then away from the listener.

Conclusion

The passage details the Doppler Effect, explaining how a higher pitch results from compressed sound waves with higher frequency. Choice B incorrectly states that higher pitch is due to low frequency, which contradicts the passage's explanation. All other choices accurately describe details about the Doppler Effect as outlined in the passage.

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