The Doppler effect refers to change in the observed frequency of a wave if the observer and source are in relative motion.
Questions tagged [doppler-effect]
561 questions
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Why doesn't the motion of a car affect the frequency of radio stations?
When we go in a car and tune to an FM radio station, why doesn't our motion disturb the frequency?
Like the Doppler effect?
DARU SRINIVAS
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Can gravitational waves be red-shifted?
Whenever the Doppler effect is mentioned, it's typically in the context of sound waves or electromagnetic radiation. On the cosmological scale, red-shifting is also important because of the enormous speed of receding galaxies, thanks to the…
HDE 226868
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Is it possible to estimate the speed of a passing vehicle using a musical ear and the doppler effect?
I've found a number of questions that concern the Doppler effect, but none that seem to address my question.
I have a background in music. People with a musical ear can generally tell the ratio between two frequencies (as a musical interval). For…
M_M
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Conservation of energy and Doppler effect?
From what I understand, the frequency of light coming from a source moving towards an observer increases. From $ E=h\nu $ , this implies an increase in the energy of each photon.
What really is confusing, is where does that extra energy come from?…
S L
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What do you really see on a line of clocks as you pass by them at high speed?
According to my understanding of SR, if I travel at 0.8c relative to a line of clocks, I should see the clocks in front of me going 3 times faster than my own, and those behind me going 3 times slower than my own (Doppler effect).
OK, so what…
m4r35n357
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trouble reconciling doppler shift for energy and momentum of light
[See final additions at bottom for a restatement of the paradox.]
I have seen the assertion in a couple of places that if you trap light in a reflective resonator, or any other kind of sealed trap, then (as another user here put it in answering a…
Paul Kienitz
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Why isn't the Doppler effect (for sound waves) symmetric with respect to source and receiver?
The Doppler effect formula is $$f = \frac{(v\pm v_r)}{(v\mp v_s)}f_0$$ where $f$ and $f_0$ are the observed and emitted frequency, respectively, and $v, v_r$ and $v_s$ the speed of the waves, receiver and source, respectively (all relative to the…
Javi
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Why do lines in atomic spectra have thickness? (Bohr's Model)
Consider the atomic spectrum (absorption) of hydrogen.
The Bohr's model postulates that there are only certain fixed orbits allowed in the atom. An atom will only be excited to a higher orbit, if it is supplied with light that precisely matches…
Gerard
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What is the relationship between relativity and the Doppler effect?
My sister just watched this video about space contraction (Spanish), and asked me if this is related to the Doppler effect.
In the clip they also introduce the idea that a bat would be affected by similar effects when measuring an object's length,…
jjmontes
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Relativity of temperature paradox
The imagined scenario:
Part A:
From special relativity we know that velocity is a relative physical quantity, that is, it is dependent on the frame of reference of choice. This means that kinetic energy is also relative, but this does not undermine…
user929304
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Can an object moving fast enough away from a stationary observer redshift out of the visible spectrum?
I ran some numbers using the relativistic longitudinal Doppler effect formula
$$\lambda_r = \sqrt{\frac{1+\beta}{1-\beta}}\cdot\lambda_s$$
where $\lambda_s$ and $\lambda_r$ are source and received wavelengths respectively, and $\beta = v/c$. Then I…
z4nc_
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Could I see the cosmic microwave background if it were Doppler shifted enough?
If I traveled fast enough, my current understanding is that visible light would be blueshifted to the blue/UV range, but also that microwaves and longer wavelength waves would be blueshifted into the visible range. Is this true? If I were to go fast…
QCD_IS_GOOD
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Relativistic Doppler effect derivation
This is about a step in a derivation of the expression for the relativistic Doppler effect.
Consider a source receding from an observer at a velocity $v$ along the line joining the two. Light is emitted at frequency $f_s$ and wavelength $\lambda_s$.…
Comp_Warrior
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Why doesn't the speed of the wind have an effect on the apparent frequency?
A boy is standing in front of stationary train. The train blows a horn of $400Hz$ frequency . If the wind is blowing from train to boy at speed at $30m/s$, the apparent frequency of sound heard by the boy will be?
The answer: The frequency remains…
Eliza
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Is it better to call the doppler effect a change in wavelength or frequency?
Why is it preferable to say that the doppler effect causes a shift in frequency rather than a shift in wavelength? I often read on websites that they define the doppler effect as a change in frequency.
user28737