If the speed of light is constant at any velocity, how do you get frequency shifts in light?

Question

Well, obviously I'm completely misunderstanding relativity here, but it seems to me that if you've got a doppler shift where there wasn't one earlier, there's got to be some change in relative velocity between the observer and the waves, Now, if an observer can change their velocity relative to light waves, then how is it that "observers will always measure the speed of light to be the same no matter what their state of uniform linear motion is"(-Wikipedia)

Answer 1

in a nutshell, speed is irrevalent,
as frequency increases, wavelength decreases,
and vice versa
same with sound

Answer 2

First of all, the speed of light is a constant only in a vacuum, it does change pretty insignificantly when it travels into denser mediums. The Doppler effect has nothing to do with the speed of a wave, just the wavelength, what happens with the Doppler effect is as the source of the light moves towards you, the wavelengths are shorter, because...well call 2 crests of a wave Point A and Point B, while the Light Source is Point C, If point A is moving in the same direction as point C, when point B is released point A and point B will be spaced closer together due to relative speed, which is never a constant, however if point A is moving AWAY from point C, then point's A and B will be spaced farther apart due to relative speed once again.

D'oh I got all through that explanation and forgot to include the fact that the points would be closer or farther apart than they would be if point C was stationary.

PS. If point A and C are moving in the same direction, then the light will be bluish, if they're moving apart, it will be reddish.

Answer 3

When the speed of light is independent of the speed of the observer, the observer measures the speed of light as always constant.

How the Doppler Effect is explained in light? In sound we use the relative speed of observer and source of sound to find the Doppler Effect.

I hope there will be some answer, but the answers in analogy with sound will not hold good.
http://www.anti-relativity.com/dopplerparadox.htm

But I hope that since C = n lambda, where n is the frequency and lambda is the wavelength, If lambda decreases n will increase so as to keep C constant.

When we move with some speed the length decreases and hence our measurement of wave length of light must decrease. Correspondingly the frequency is increased.

In that case there will be always increase in frequency and no decrease of frequency in the case of light.

Answer 4

Okay!i got your doubt!
First of all come to the great einstein`s brave postulate-"The speed of the light is constant or same in all direction and is independent of the inertial frame chosen".Right?
And another misconception with you is"speed of light is constant at any velocity"what that sentence means?Speed and velocity are equal for the speed of the light since it is not a vector and it is never obeys the vector laws then how come you call it has a vector quantity?i.e velocity.So you should know that light has only speed and has no direction that's what the Einstein`s theory says! and coming to your question,hm.......
yes!i understood your point!first of all you should know that frequency is a function of the wave and not the medium,right?i hope you know this!then about your point the Doppler shift when occur in waves that travel with less speed than the speed of light the relative velocity changes.But this is the question where Einstein taken the scientific world for a ride!that is his brave postulate!The speed of light is the maximum and even if there is a velocity that should be added the sapped of light it is taken same as that of speed of light since for example if you are travelling on a bus and thrown a ball then the ball has your thrown velocity+the bus velocity but as you see it in the case of light if you focus a light beam from that bus the light ray should have its only speed i.e the value "c".Got it?There is no upper limit to the speed of light and no upper limit to its kinetic energy!and it travels in vacuum with a velocity of value "c" speed of light is not affected by any external source and the uniform linear motion according to the wilipedia definition is true always.The Einstein`s theory of relativity is all about it!make the point see clear"any inertial frame of reference the spped of light is same",so any direction the spped is equal and even any frame the observer see is equal!and even an observer changes his relative velocity with the light as from theory of relativity the frame changes and the "shift" is such apparent that it is almost negligible!
i hope this would make your question prove quite nicely!
have a nice day!

Answer 5

I think that is a misstatement about the observer. Obviously, if the observer speeds up and moves away, then light will not adjust itself to always appear constant.
What they meant was that relative to the light itself, the speed is a constant. To an observer, with Doppler shifts, etc., it is obvious that there is a RELATIVE change in the linear uniform motion of light secondary to the change in the position of the observer.

Answer 6

As a wave, light travels the same speed it does a wave, the constant C. In the equation velocity=fequency x wavelength, when the velocity remains the same, the only things that can change are the wavelengths and frequency of the wave.

So if the wavelength of a photon particle is longer, as it is in infra-red, the frequency is shorter, keeping the velocity at C.

Basically, a photon travels at the same speed, but fluctuates in a different dimension (to the left and right or up and down) at different time intervals and of different wavelengths.

Answer 7

As far as i know, frequency only affects color and intensity of light but not velocity.
"observers will always measure the speed of light to be the same no matter what their state of uniform linear motion is"- this might happen only if their velocity is not to close to speed of light

Answer 8

Frequency is related to wave length. As the wave length is lengthened the the frequency is slowed and vise versa. The speed of the wave is independent of either F or W and is dependent of the medium through which it travels. Thus you can have a f-shift and yet the speed of the wave will remain the same.

Answer 9

That's actually one of the illuminating consequences of special relativity. The light beam will travel at the same speed "speed", but have a shifted frequency. Since frequency is oscillations per unit time, this implies that someone who moves at a different velocity will be counting time differently from you, which is actually true.

The easiest to grasp argument is the light beam in a railcar thought experiment.

Answer 10

typically relativity, you kind the impression of gravity as a stretching of area/time. notwithstanding that is a postulate of GR (assumed from the initiating) that mild travels at a p.c. c. so as area is stretched, so is time. because the wavelength of sunshine vacationing through a stretched area is going up, the frequency is going down. that is the gravitational redshift we word. All that stated, some thing humorous exceeded off early interior the universe. The universe and each little thing in it seems that to have speeded up a lot a lot swifter than the speed of sunshine. So who's easily-known with truly--perchance there is one of those mechanism.

Answer 11

The trick in special relativity is that no matter which inertial reference frame you pick you get the same answer. If someone is moving away from you or you are moving away from them you get a red shift or a lower frequency. The same is true with sound the only difference is with sound there is a preferred reference frame to do the calculations, with light there isn't.