HESI A2 VERSION 1 READING COMPEHENSION Doppler Effect 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 fastapproaching modes of transportation distance themselves past the listener, who hears a lower pitch. 1. Which statement is not listed as a detail in the passage? A. The oncoming sound waves have a higher pitch because of high frequency and closeness of waves. B. The oncoming sound waves have a higher pitch because of low frequency and closeness of waves. C. The whistling sound of the locomotive as it approaches and passes can be explained by the Doppler effect. D. The high-pitched sound of the ambulance as it approaches and passes can be explained by the Doppler effect. 2. What is the main idea of the passage? A. Trains and ambulances make distinctly loud noises. B. Low-frequency waves make high-pitched sounds. C. High-frequency waves make low-pitched sounds. D. The Doppler Effect explains the rationale for why sound is heard initially more strongly and then faintly after a moving object has passed. 3. What is the meaning of the word phenomenon in the second paragraph? A. Something that is lifeless to the senses B. Something that is nonchalant C. Something that is significant but unusual D. Something that is chemical in origin 4. What is the author’s primary purpose in writing this essay? A. To entertain the reader with information about trains and ambulances B. To inform the reader about avoiding accidents, which involve trains and ambulances C. To inform the reader about how movement affects sound D. To analyze the difference between train and ambulance sounds 5. Which sound waves have a higher pitch? A. Those waves that are closer together B. Those waves that are farther apart C. Those waves that travel a long distance D. Those waves that travel a short distance 6. Which sound waves have a lower pitch? A. Those waves that are closer together B. Those waves that are farther apart C. Those waves that travel a long distance D. Those waves that travel a short distance