Relativistic Doppler Effect - Arbitrary Velocity

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SUMMARY

The discussion focuses on the relativistic Doppler effect, specifically how to calculate the observed frequency (ν) in terms of proper frequency (ν₀), speed (v), and radial velocity component (vᵣ) for a source moving with respect to an observer. The equations provided include ν = γν₀ and E = γE₀, where γ is the Lorentz factor. The conversation highlights the distinction between relativistic and non-relativistic Doppler shifts, emphasizing that frequency changes can occur even when the source is not moving directly towards or away from the observer due to time dilation effects.

PREREQUISITES
  • Understanding of the Lorentz factor (γ) in special relativity
  • Familiarity with the concepts of frequency and energy in physics
  • Knowledge of the Doppler effect in both classical and relativistic contexts
  • Basic understanding of vector components in motion
NEXT STEPS
  • Study the derivation of the Lorentz factor (γ) in special relativity
  • Explore the implications of time dilation on observed frequencies
  • Learn about the non-relativistic Doppler effect for comparison
  • Investigate applications of the relativistic Doppler effect in astrophysics
USEFUL FOR

Students and educators in physics, particularly those studying special relativity and wave phenomena, as well as professionals in fields such as astrophysics and engineering who require a deep understanding of frequency shifts due to relative motion.

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Homework Statement



Find the observed frequency ##\nu## in terms of proper frequency ##\nu_0##, speed ##v## and radial velocity component ##v_r## for a source moving at velocity ##\vec v## with respect to the observer.

Now consider an observer in frame S where the source is seen moving at speed ##\vec v## along x-axis and at ##y=y_0##. At ##t=0##, the source is seen to emit frequency in ##-\hat y## direction. Find energy detected by the observer in terms of ##E_0## and ##|v|##.

Homework Equations

The Attempt at a Solution



Part(a)
Not sure how to approach this part. We've always done problems in standard configuration..


Part (b)

2010_B2_Q6.png


\nu = \gamma \nu_0
E = \gamma E_0 = \frac{E_0}{\sqrt{1 - \frac{v^2}{c^2}}}

Is this too easy to be true?
 
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That's right. If you think about it, this differs from the non-relativistic Doppler shift because at t=0, the source isn't moving toward or away from the observer, yet you still see a change in frequency.
 
vela said:
That's right. If you think about it, this differs from the non-relativistic Doppler shift because at t=0, the source isn't moving toward or away from the observer, yet you still see a change in frequency.

Yeah I thought so too, it's just a manifestation of time dilation (which is independent of how far you are away in the non-general relativity context).

Any tips on part (a)?
 
bumpp
 

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