Causes Of Doppler Effects

Answer 1

Take a deep breath and read through this. Doppler effect happens because there is relative motion between a wave source and an observer, and this changes the "rate" at which the crests and troughs of the wave arrive at the observer, and, therefore, the period of the wave. That's why it happens, so now let's translate it. We'll assume a source and an observer, and then take it from there. When a wave source, whether the wave is light (electromagnetic) or sound (mechanical) or other, the wave leaves the source and travels to the observer. If there is no relative motion between the source and observer, that is, if the distance between them is not increasing or decreasing, then the wave arrives at the observer as it left the source. There will be crests and troughs arriving "on schedule" according to the period of the wave. The period of a wave, you'll recall, is the time it takes for one complete cycle of the wave. Anyway, crests will be arriving (each followed by a trough) one after the other with a fixed amount of time between them (the period) that was dictated by the source. Now let's look at the picture with some relative motion. With the distance between the source and observer decreasing because one or both is moving and they are getting closer, something happens to the "timing" of the wave. Remember that the crests were arriving with a fixed amount of time between them, which was the period of the wave. When the the distance between the source and observer is decreasing, the observer can be seen to be moving "toward" the next crest. The observer is "hurrying to meet" the next crest, and will "get to the crest" before it would have gotten to him if he was just waiting for it. Make sense? Let's look at it another way. The time between the arriving crests as seen by an observer who is moving toward a source is shorter than it would be if he was just "waiting" for the next crest to arrive. He'll "go to meet it" and the period will be shorter. The shorter period translates into a high frequency. And even though the source is not creating the wave at that higher frequency, the observer is still observing (seeing or hearing) the wave at that higher frequency. The observation is "real" in that if the period of the wave is measured, it is shorter than it was. The change in the frequency, that shift in the frequency of the wave, is called Doppler shift. And it's really that simple.

Answer 2

Doppler effects are illusionary distortions to a waveform caused by the relative motion of the signal source and the signal detector. The wavelength seems shorter than it actually is when the two are moving toward one another, and longer when the two are moving away from one another. For sounds, an approaching sound emitter will sound higher in pitch than it actually is, and a retreating sound emitter will sound lower in pitch. In the case of visually detected objects, approaching objects will seem to be a bluish color, and retreating objects will seem to be a reddish color... though it should be noted that, due to the high speed of light waves, this effect is only noticable at extremely high movement speeds over astronomical distances, or using spectrographic detectors millions of times more sensitive than the human eye.

Answer 3

The Doppler effect occurs when there is a change in frequency or wavelength of a wave due to relative motion between the source of the wave and the observer. This can be caused by the source or the observer moving towards or away from each other. The effect is commonly observed in sound waves, light waves, and other forms of wave propagation.