Question

The Doppler Effect on frequency doesn’t depend on:
A) The frequency of the wave produced
B) The speed of source
C) The distance between source and observer
D) The speed observer

Answer 1

Hint: To answer this question we should first know what the Doppler Effect is. Then we can use the formulae of frequency, as observed by the observer when the source and observer are moving or any one of them is moving, to find the change in frequency. The variables on which this change depends will give us the answer.

Formulae used:
$f' = f\left( {\dfrac{{v \pm {v_o}}}{{v \pm {v_s}}}} \right)$
Here $f'$ is the frequency received by the observer, $f$ actual frequency of the sound, $v$ is the speed of sound, ${v_o}$ is the speed of the observer and ${v_s}$ is the speed of source.

Complete answer:
To answer this question, we should first know what the Doppler Effect in frequency is. Doppler Effect can be defined as the change in the frequency of the sound wave due to the movement of the observer toward or away from the source or the movement of the source toward or away from the observer. The changed frequency in the sound is given by,
$ \Rightarrow f' = f\left( {\dfrac{{v \pm {v_o}}}{{v \pm {v_s}}}} \right)$
Here $f'$ is the frequency received by the observer, $f$ actual frequency of the sound, $v$ is the speed of sound, ${v_o}$ is the speed of the observer, and ${v_s}$ is the speed of the source.

Thus we can say that the new frequency depends on the original frequency of the sound source, the speed of sound, the speed of the observer, and the speed of source. So the frequency does not depend on the distance between the source and observer. Similarly, the change in frequency is independent of the distance between the source and observer.

So option (C) is the correct answer.

Note: The Doppler Effect is a common effect which can be observed in our day to day life. The most common example can be observed on the road. Whenever a vehicle approaches us, the pitch of the horn is higher for a fast-moving vehicle as compared to a slow-moving vehicle. The Doppler Effect is very useful in the field of robotics, sirens, radar, astronomy, etc.