Question

A fire truck emits sound waves at a constant frequency. An observer stands

several blocks away. Which statement best describes the sound waves
perceived by the observer as the fire truck approaches?
The wavelength and frequency both decrease.
The wavelength decreases and the frequency increases.
The frequency and wavelength remain the same.
The wavelength increases and the frequency decreases.

Answer 1

The sound waves perceived by the observer as the fire truck approaches have a decreased wavelength and an increased frequency.

Step-by-step explanation:

The observer standing several blocks away perceives the sound waves emitted by the approaching fire truck to have a decreased wavelength and an increased frequency. As the fire truck moves closer, the air compressions become closer together in the direction of its motion, resulting in a shorter wavelength and higher frequency. On the other hand, the air compressions become farther apart in the opposite direction of motion, leading to a longer wavelength and lower frequency.