Question

The sound of a police siren that is moving away has (1) _____ wavelengths, and one that is approaching has (2) ______ wavelengths.

1) a. longer b. higher c. shorter

2) a. lower b. Longer c. shorter

Answer 1

FIRST one (shorter)

SECOND one (longer)

Answer 2

Answer;

A. Longer

C. Shorter

The sound of a police siren that is moving away has shorter wavelengths, and one that is approaching has longer wavelengths.

Explanation;

• The pitch of the sound heard depends on the frequency of the sound wave. A higher frequency corresponds to a high pitch. Therefore, when the police siren is approaching an observer, the observed frequency increases and thus the observer hears a higher pitch.
• Conversely, when the police siren is moving away from an observer, then the frequency decreases and thus, the pitch of the sound heard is lower.

• A higher frequency corresponds to a shorter wavelength, therefore, the shorter the wavelength, the higher the frequency, and the higher the pitch, of the sound.