Relativistic Doppler Effect - Arbitrary Velocity

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Homework Help Overview

The problem involves the relativistic Doppler effect, specifically determining the observed frequency and energy detected by an observer when a source is moving at an arbitrary velocity. The context includes considerations of proper frequency and the effects of relativistic speeds on frequency and energy measurements.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster expresses uncertainty about how to approach the first part of the problem, noting a departure from standard configurations. They provide a formula for the observed frequency and energy in the second part but question the validity of their findings. Other participants reflect on the differences between relativistic and non-relativistic Doppler shifts and mention time dilation as a factor.

Discussion Status

The discussion is ongoing, with participants exploring the implications of the relativistic Doppler effect. Some guidance has been offered regarding the conceptual differences from non-relativistic cases, but there is no explicit consensus on how to tackle the first part of the problem.

Contextual Notes

Participants are navigating the complexities of relativistic effects and questioning assumptions about the motion of the source relative to the observer, particularly at the initial time of emission.

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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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