Originally posted by amrit23
first of all..thnx alot for opening such a thread n that too on a subject like physics..
i was just wondering if u culd explain to me why is doppler's effect in sound asymmetric
also..does anybody know any short cuts to the physics numericals
im just unable to solve them..
Once you understand fundamentals well, then solving numericals is easy. The following site is maintained by me. You can post questions there if you need any help.
Dopper effect is asymmetric is because when the source is moving and the object is stationary, then the wavelength emitted by the source changes. As an analogy, suppose I throw one ball every at fixed time interval (say T). Since we are using this as an analogy of wave, let us ignore gravity or any other force. Suppose I have thrown 10 balls. If I am at rest, then distance between 1st and 2nd balls is the same as the distance between 2nd and 3rd balls and so on. But if I am moving and as earlier I throw balls at interval of T, then the balls will not be evenly spaced. This is same as saying that wavelength changes. But speed of sound relative to observer remains the same because the observer is at rest. Frequency = speed/wavelength. The speed is the same but the wavelength is different. This results in change in observed frequency.
But when source is at rest and observer is moving, then the source sees its waves evenly spaced. Thus wavelength emitted by the source remains the same. But speed of sound relative to observer changes. Frequency = speed/wavelength. The
wavelength is the same but the speed is different. This results in
change in observed frequency.
Thus in one case, Doppler effect is due to change in wavelength and in another case due to change in sound's speed relative to the observer. That is why the results are different.