Which of the following statements is true of vibrations? Question 3 options: A) Ultrasonic vibrations have a frequency lower than the range for normal hearing. 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) Neither ultrasonic nor infrasonic vibrations can be heard by humans.
The Correct Answer and Explanation is:
Correct Answer: D) Neither ultrasonic nor infrasonic vibrations can be heard by humans.
Explanation:
Vibrations are oscillations that travel through a medium like air, water, or solids. When these vibrations travel through the air, they can be detected by the human ear if they fall within a specific frequency range. This range for average human hearing is approximately 20 Hz to 20,000 Hz (20 kHz).
Let’s evaluate each option:
- Option A is false. It says ultrasonic vibrations have a frequency lower than the range for normal hearing. That is incorrect. Ultrasonic vibrations actually have a frequency higher than 20,000 Hz, which is above the normal range for human hearing.
- Option B is false. It states that infrasonic vibrations have a frequency that is too high to be heard by humans. This is the opposite of the truth. Infrasonic vibrations are those that are below 20 Hz, so they are too low, not high, to be heard by humans.
- Option C is false. It incorrectly claims that infrasonic vibrations are used in sonar equipment and flaw detection. In reality, those technologies use ultrasonic vibrations, which can penetrate materials and reflect back, revealing structural features.
- Option D is true. Ultrasonic vibrations (above 20,000 Hz) and infrasonic vibrations (below 20 Hz) are both outside the normal range of human hearing. Therefore, neither can be heard by the average human ear.
In summary, the human ear is limited to a specific frequency range, and vibrations outside this range are classified as either infrasonic (too low) or ultrasonic (too high). Because both are beyond human perception, option D is the correct statement about vibrations.
