When measuring the speed of sound, which law is often applied?

• A. Bernoulli's law
• B. Poiseuille's law
• C. Snell's law
• D. Doppler's law

Answer: (D)

Doppler's law is relevant in measuring the speed of sound as it describes the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. This principle is applied frequently in various contexts, including sound.

When an observer moves toward a sound source, the frequency of the sound waves increases, leading to a higher perceived pitch. Conversely, if the observer moves away from the source, the frequency appears lower. By measuring these shifts in frequency, one can determine the speed of sound in a given medium.

Using Doppler's law facilitates the understanding of how sound waves propagate and change in frequency based on relative motion, making it a powerful tool in acoustics.