Why does the amplitude of a sound wave decrease with distance from its sou – [Free] B91
Why does the amplitude of a sound wave decrease with distance from its source? Question 6 options: A.The amplitude of a sound wave decreases with distance from its source, because the frequency of the sound wave decreases. B.The amplitude of a sound wave decreases with distance from its source, because the speed of the sound wave decreases. C.The amplitude of a sound wave decreases with distance from its source, because the wavelength of the sound wave increases. D.The amplitude of a sound wave decreases with distance from its source, because the energy of the wave is spread over a larger and larger area.
Why Does the Amplitude of a Sound Wave Decrease With Distance?
Question:
Why does the amplitude of a sound wave decrease with distance from its source?
- A. The wavelength of the sound wave increases
- B. The energy of the wave is spread over a larger and larger area
- C. The speed of the wave decreases
- D. The frequency of the sound wave decreases
Answer:
Correct Answer: B – The energy of the wave is spread over a larger and larger area.
Explanation:
When a sound wave travels outward from its source, it radiates in all directions. As the wave moves farther, it covers an increasingly larger spherical area.
This means that the energy per unit area (also known as energy density) decreases with distance. The total energy remains the same, but it’s distributed over more space.
Since the amplitude of a sound wave is directly related to the energy it carries (with energy being proportional to the square of the amplitude), a decrease in energy density results in a decrease in amplitude as perceived by a listener.
Key Concept:
Amplitude is proportional to the square root of energy density. As the energy spreads out with distance, the energy density and therefore amplitude decrease.
Why Other Options Are Incorrect:
- A. Wavelength increase: Not directly related to amplitude reduction.
- C. Speed decrease: The speed of sound remains constant in a given medium.
- D. Frequency decrease: Frequency of the sound wave is constant and does not depend on distance.