Question

doppler effect with trains. the image shows a stationary train indicated by letter a and a moving train, indicated by letter b. if the person standing at the train station hears sounds coming from both trains, which explanation best predicts the changes in sound being observed by the person in the model? a the frequency of the sound from train a and train b will remain the same with regard to the observer. b the frequency of the sound from train a will increase and the frequency of the sound from train b will decrease with regard to the observer. c the frequency of the sound from train a will decrease and the frequency of the sound from train b will increase with regard to the observer. d the frequency of the sound from train a will remain the same and the frequency of the sound from train b will decrease with regard to the observer.

Explanation:

The Doppler - effect states that when a source of sound is moving relative to an observer, the frequency of the sound changes for the observer. For a stationary source (train A), the frequency of the sound remains the same as the actual frequency of the source because there is no relative motion between the source and the observer. For a moving source (train B), as it moves away from the observer, the sound waves get stretched out, resulting in a decrease in frequency heard by the observer.

Answer:

D. The frequency of the sound from train A will remain the same and the frequency of the sound from train B will decrease with regard to the observer.