HESI A2
VERSION 1
READING COMPEHENSION
Doppler Effect
Have you ever wondered why the whistle of a traveling distant locomotive
predicts its approachseveral yards before anyone actually sees it? Or why an
oncoming a
...
HESI A2
VERSION 1
READING COMPEHENSION
Doppler Effect
Have you ever wondered why the whistle of a traveling distant locomotive
predicts its approachseveral yards before anyone actually sees it? Or why an
oncoming ambulance’s screaming sirenis 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 towardthe 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 higherpitch. 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.
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 closenessof waves.
B. The oncoming sound waves have a higher pitch because of low frequency
and closenessof waves.
C. The whistling sound of the locomotive as it approaches and passes can be
explained bythe Doppler effect.
D. The high-pitched sound of the ambulance as it approaches and passes
can be explainedby 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 stronglyand then faintly after a moving object has passed.
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