Question 16

The Doppler Effect explains why sound is heard more strongly initially and then faintly after a moving object has passed.

The passage primarily discusses the Doppler Effect and how it relates to the perception of sound from moving objects such as trains and ambulances. It explains how the sound waves behave differently based on the movement of these objects, leading to variations in pitch and volume as they approach and then recede.

A) Trains and ambulances emit loud noises.

While trains and ambulances do emit loud noises, this statement does not capture the central concept of the passage. The passage focuses on the phenomenon of the Doppler Effect, which is not solely about the volume of sounds but rather about how the frequency of sound waves changes based on the movement of the source relative to the listener.

B) Low-frequency waves produce high-pitched sounds.

This statement is incorrect. The passage indicates that as sound waves are compressed when a sound source approaches, they result in a higher frequency and thus a higher pitch. Low-frequency waves would not produce high-pitched sounds; rather, they produce lower pitches, contradicting the core explanation provided in the text.

C) High-frequency waves result in low-pitched sounds.

This option is also incorrect. The passage explains that high-frequency waves are associated with higher-pitched sounds when the source is approaching. This option misrepresents the relationship between frequency and pitch, making it inconsistent with the information provided in the passage.

D) The Doppler Effect explains why sound is heard more strongly initially and then faintly after a moving object has passed.

This statement accurately encapsulates the main idea of the passage. It succinctly describes the Doppler Effect and how it accounts for the changes in sound perception based on the movement of the source relative to the listener, highlighting the initial stronger sound followed by a fading one.

Conclusion

Option D is the most accurate representation of the passage's main idea, effectively summarizing the explanation of the Doppler Effect and its impact on sound perception. All other options either misinterpret the relationship between sound frequency and pitch or fail to address the scientific phenomenon discussed, making them incorrect in the context of the passage.