Question

if a train is moving away from an observer, what kind of sound will the observer hear from the train whistle? a it will appear to be lower in pitch than the actual train whistle b it will appear to be higher in pitch than the actual train whistle c it will sound the same as the actual train whistle d it will sound louder than the actual train whistle e none of the above

Explanation:

This problem is related to the Doppler effect in Physics. The Doppler effect describes the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. When the train (source of sound) is moving away from the observer, the wavelength of the sound waves emitted by the train whistle gets stretched. Since pitch is related to frequency (\(f=\frac{v}{\lambda}\), where \(v\) is the speed of sound and \(\lambda\) is the wavelength), a longer wavelength (\(\lambda\)) results in a lower frequency (\(f\)). So the observer will hear a sound that is lower in pitch than the actual train whistle.

Answer:

A. It will appear to be lower in pitch than the actual train whistle