Quick 'n' easy question about doppler effect

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Discussion Overview

The discussion revolves around the Doppler effect, specifically its formula and its application to light and electromagnetic waves. Participants explore the differences between classical and relativistic interpretations of the Doppler effect, as well as the derivation of relevant equations.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether the Doppler effect formula "f=f0((v+vo)/(v+vs))" is derived from classical speed addition, suggesting this may explain differences in the Doppler effect for light and EM waves.
  • Another participant asserts that light does not behave as a classical particle, emphasizing that it maintains a constant speed for all observers, with frequency and wavelength undergoing a Doppler shift.
  • A participant expresses confusion regarding the derivation of the relativistic Doppler effect equation as presented on a specific webpage, indicating a lack of clarity on its formulation and expansion using Maple software.
  • Another reply clarifies that the equation in question is a rewritten form of the relativistic Doppler formula, intended for deriving the low-speed approximation, and provides an equivalent expression for comparison.

Areas of Agreement / Disagreement

Participants express differing views on the derivation and interpretation of the Doppler effect equations, indicating that multiple competing views remain and the discussion is unresolved.

Contextual Notes

Some participants reference specific forms of the Doppler effect equations and their equivalences, but there is uncertainty regarding the derivation process and the application of software tools for expansion.

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Doppler effect revisited

Am I right when I say that the doppler effect formula "f=f0((v+vo)/(v+vs))" is derivated from the classical theorem of speed addition and this is why the doppler effect for light and EM waves is different?
 
Last edited:
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Because light does not behave as a classical particle, it has a constant speed for all observers. It is frequency and wavelength which undergo a Doppler shift in light.
 
I'm a little confused here...

I don't get how on this page: hyperphysics they get the first equation... I don't see the relativistic doppler effect written that way anywhere and I don't understand how they get ot that equation and how to expand it with maple...Anybody can help?
 
That equation is just the relativistic Doppler formula rewritten in a form convenient for deriving the low speed approximation. They took something that usually appears in a form like:
[tex]\sqrt{\frac{1 + x}{1 - x}}[/tex]
And rewrote it like:
[tex]\frac{\sqrt{1 - x^2}}{1 - x}[/tex]
These expressions are equivalent.
 

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