AAMC FL Practice Exam

What is the formula for the observed frequency in the Doppler effect?

1. f' = (V + V0)/(V - Vs) * f

2. f' = (V - V0)/(V + Vs) * f

3. f' = V * f

4. f' = f/(V + Vs)

The correct answer is: f' = (V + V0)/(V - Vs) * f

The formula for the observed frequency in the Doppler effect accounts for the movement of the source and observer relative to each other. The correct formula describes how the frequency of a wave changes due to the relative motion between the source of the wave and the observer. In this formula: - \( f' \) represents the observed frequency. - \( f \) is the actual emitted frequency of the wave. - \( V \) is the speed of the wave in the medium (for sound waves, this is the speed of sound). - \( V_0 \) is the speed of the observer relative to the medium. - \( V_s \) is the speed of the source relative to the medium. The formula indicates that when the observer moves towards the source (with the term V + V0), the observed frequency increases, as the waves are compressed. Conversely, when the source moves away from the observer (with the term V - Vs), the observed frequency decreases since the waves are stretched. This relationship between speed and frequency explains the change in frequency based on the motion of both the source and the observer, uniquely characterizing the Doppler effect. This makes the correlation with observed frequency particularly relevant in contexts like astronomy or radar where relative motion affects