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# Intuitive understanding of doppler effect

I think everyone knows what doppler effect exactly is. I wish to write what I understood about doppler effect intuitively. If you think that I am wrong you can correct me.

Assume that a wave is coming towards you. It's time period is T seconds. Now the frequency that you see will be

f=1/T.

Now assume that you are moving towards the wave. As you move towards the wave you can clearly see that you would traverse an entire wave (ie wavelength) sooner when compared to the previous case (you were standing before). As you traverse the entire wavelength of the wave sooner, the time period that you perceive for that wave decreases. So the frequency increases.

Similarly when you move away from the wave the frequency decreases.

Note that nothing has happened to the original wave's frequency (i.e. frequency of the wave at the source has not changed) but what you received has changed because of your movement.

Hence Doppler effect is a direct consequence of theory of relativity. It stresses on the fact that your movement plays a vital role in any physical phenomenon.

Do you think what I am telling is impossible? Okay, then read this. I think everyone knows that when air particles hit our ears we hear the sound. That sound depends on the frequency with which the air particles hit our ears. When you are moving, these particles will complete one wave (ie one wavelength) sooner than when you stand. That is, these particles hit your ear with a frequency which is different from it's original frequency (i.e. at it's source). In other words the frequency of the wave as seen by your ear has changed. Hence you hear different sounds when a train approaches and when it goes past you.

Doppler effect is the best example for theory of relativity.

Doppler effect plays a vital role in the bandwidth. The frequency of the wave that you have received has indeed changed. As the frequency changes, the bandwidth of the wave also changes, so that when you pass that wave through a filter there are many possibilities for distortion if you don't take Doppler effect into consideration.

Regards,
iVenky.

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iVenky