Have you ever wondered whythe whistle of a traveling, distant locomotive predicts its approach
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several yards before anyone actually sees it? Or why an oncoming ambulance’s screaming siren is
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heard momentarily several feet before the ambulance comes into full view, before it passes you,
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and why its siren is still heard faintly well after the ambulance is out of sight?
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What you are witnessing is a scientific phenomenon known as the Doppler Effect. What takes
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place is truly remarkable. In both of these instances, when the train or ambulance moves toward the
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sound waves in front of it, the sound waves are pulled closer together and have a higher frequency.
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In either instance, the listener positioned in front of the moving object hears a higher pitch. The
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ambulance and locomotive are progressively moving away from the sound waves behind them,
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causing the waves to be farther apart and to have a lower frequency. These fast- approaching
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modes of transportation distance themselves past the listener, who hears a lower pitch.
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1. Which statement is not listed as a detail in the passage?
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A. The oncoming sound waves have a higher pitch because of high frequency and closeness of
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waves.
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B. The oncoming sound waves have a higher pitch because of low frequency and closeness of
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waves.
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C. The whistling sound of the locomotive as it approaches and passes can be explained by the
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Doppler effect.
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D. The high-pitched sound of the ambulance as it approaches and passes can be explained by
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the Doppler effect.
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2. What is the main idea of the passage? t t t t t t t
A. Trains and ambulances make distinctly loud noises.
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B. Low-frequency waves make high-pitched sounds. t t t t
C. High-frequency waves make low-pitched sounds. t t t t
D. The Doppler Effect explains the rationale for why sound is heard initially more strongly
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and then faintly after a moving object has passed.
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3. What is the meaning of the word phenomenon in the second paragraph?
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,A. Something that is lifeless to the senses
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, B. Something that is nonchalant t t t
C. Something that is significant but unusual t t t t t
D. Something that is chemical in origin t t t t t
4. What is the author’s primarypurpose in writing this essay?
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A. To entertain the reader with information about trains and ambulances
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B. To inform the reader about avoiding accidents, which involve trains and ambulances
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C. To inform the reader about how movement affects sound
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D. To analyze the difference between train and ambulance sounds
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5. Which sound waves have a higher pitch?
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A. Those waves that are closer together
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B. Those waves that are farther apart
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C. Those waves that travel a long distance
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D. Those waves that travel a short distance
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6. Which sound waves have a lower pitch?
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A. Those waves that are closer together
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B. Those waves that are farther apart
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C. Those waves that travel a long distance
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D. Those waves that travel a short distance
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Electrocardiogram
Beep!…Beep!…Beep! is the audible rhythmic sound made as the strength of the heart muscle is t t t t t t t t t t t t t t
measured. The signal cadence has a characteristic record that varies in every individual. This
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record is called an electrocardiogram, or ECG.
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In the body, an array of systemic neural responses constantly occur, emitting electric currents. The
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electric currents can be detected on the surface of the body, and if a person is hooked to an amplifier,
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these impulses are recorded by an electrocardiograph.
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Most of the information obtained is about the heart because the heart sends out electric currents in
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waves. This ―wave of excitation‖ spreads through the heart wall and is accompanied by
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electric changes. The wave takes place in three distinct steps.
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