Special Relativity: Rocket Signal Reception Time and Frequency Shift

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Homework Help Overview

The discussion revolves around a problem in special relativity involving a rocket traveling at a significant fraction of the speed of light (0.6c) relative to a space station. The original poster is tasked with determining the time it takes for the rocket to receive a specific number of signals, considering the effects of time dilation and the relativistic Doppler effect.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply concepts of time dilation and the Doppler effect but expresses confusion about the relationship between the time periods observed in different frames. Some participants question the consistency of the wavelength data with the given speed, while others suggest using the relativistic Doppler effect formula for clarification.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. Some guidance has been offered regarding the application of the relativistic Doppler effect, but there is no explicit consensus on the correct approach or resolution of the inconsistencies noted.

Contextual Notes

Participants are grappling with the implications of time dilation and the relativistic effects on signal reception, as well as the potential inconsistencies in the provided data regarding wavelength and speed. The original poster has referenced previous parts of the question that may not align with the current parameters.

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Homework Statement


A rocket of proper length 100m travels at a speed 0.6c relative to a space station, which is on the rocket’s flight path.

I have so far had to work out that:
According to an observer on the space station, the nose of the rocket is a distance of 200m away from the station upon receiving the signal. This occurs at a time t=200/c, and that light of wavelength 500nm emitted from the station is observed at 1000nm in the rocket frame.

The space station continues to transmit signals every second (according to its own clock). At what time has the rocket received 500 signals as measured by its own clock? How many signals according to an observer on the space station have been transmitted during the corresponding time period?

Homework Equations


Length contraction, time dilation, relativistic doppler effect.

The Attempt at a Solution


I'm very confused about this, as it seems to be a simple doppler effect problem to me. I.e the 1 second time period translates to 2 seconds in the rocket frame, and then the rocket has received 500 signals after 1000s in its frame. However this isn't right...
 
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according to the ship, the station clock runs slow.
 
Simon Bridge said:
according to the ship, the station clock runs slow.

In the station frame, a signal is emitted every t'=1s - this is a proper time. The lorentz factor γ=1.25 here. Therefore somebody on the spaceship sees the signals emitted every γt'=1.25s, i.e the time is dilated. Isn't this true?
 
Anybody?
 
This problem is overdetermined and inconsistent. The wavelength data is not consistent with the relative speed data. Try using the Relativistic Doppler effect formula.
 
dauto said:
This problem is overdetermined and inconsistent. The wavelength data is not consistent with the relative speed data. Try using the Relativistic Doppler effect formula.

Hmm those are previous parts to the question that I have already answered. How is the wavelength inconsistent with the speed data?

λ=λ'√(1+β)/√(1-β)
β=0.6
λ=2λ'
λ=2*500nm
λ=1000nm
 

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