Question

exam lesson name: light and sound
exam number: 700699rr
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question 5 of 20 :
select the best answer for the question.

1. which of the following statements is true of vibrations?

○ a. neither ultrasonic nor infrasonic vibrations can be heard by humans.
○ b. the frequency of infrasonic vibrations is much too high to be heard by humans.
○ c. infrasonic vibrations are used in sonar equipment and to detect flaws in steel castings.
○ d. ultrasonic vibrations have a frequency lower than the range for normal hearing.

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Explanation:

To solve this, we analyze each option:

• Option A: Human hearing range is about 20 - 20,000 Hz. Ultrasonic (above 20,000 Hz) and infrasonic (below 20 Hz) are outside this range, so humans can't hear them. This is correct.
• Option B: Infrasonic has low frequency (below 20 Hz), not high. So this is wrong.
• Option C: Ultrasonic (not infrasonic) is used in sonar and flaw detection. So this is wrong.
• Option D: Ultrasonic has frequency higher (not lower) than normal hearing range. So this is wrong.

Answer:

A. Neither ultrasonic nor infrasonic vibrations can be heard by humans.