Question

$\bullet$ Predict/Calculate The frequency of light reaching Earth from a particular galaxy is 15$\%$ lower than the frequency the light had when it was emitted. (a) Is this galaxy moving toward or away from Earth? Explain. (b) What is the speed of this galaxy relative to the Earth? Give your answer as a fraction of the speed of light.

Name: Problem 13, Chapter 25: Physics
Uploaded: 2020-02-11T09:22:39-08:00
Duration: 2 min 20 s
Channel: Alex Moore
Description: ∙Predict/Calculate The frequency of light reaching Earth from a particular galaxy is 15% lower than the frequency the light had when it was emitted. (a) Is this galaxy moving toward or away from Earth? Explain. (b) What is the speed of this galaxy relative to the Earth? Give your answer as a fraction of the speed of light.

   $\bullet$ Predict/Calculate The frequency of light reaching Earth from
a particular galaxy is 15$\%$ lower than the frequency the light had
when it was emitted. (a) Is this galaxy moving toward or away
from Earth? Explain. (b) What is the speed of this galaxy relative
to the Earth? Give your answer as a fraction of the speed of light.

Physics

James S. Walker 5th Edition

Chapter 25, Problem 13

Instant Answer

Solved by Expert Alex Moore

02/11/2020

Step 1

This can be represented mathematically as $f_{\text{earth}} = f_{\text{galaxy}}(1 - 0.15)$, where $f_{\text{earth}}$ is the frequency of light reaching Earth and $f_{\text{galaxy}}$ is the frequency of light when it was emitted from the galaxy. Show more…

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$\bullet$ Predict/Calculate The frequency of light reaching Earth from a particular galaxy is 15$\%$ lower than the frequency the light had when it was emitted. (a) Is this galaxy moving toward or away from Earth? Explain. (b) What is the speed of this galaxy relative to the Earth? Give your answer as a fraction of the speed of light.

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Key Concepts

Redshift

Redshift refers to the phenomenon where the observed frequency of radiation (such as light) from an object is lower than the emitted frequency, indicating that the source is moving away from the observer. In astrophysics, redshift is an essential concept for understanding the motion of galaxies and the expansion of the universe.

Relativistic Doppler Effect

The relativistic Doppler effect describes the change in frequency of light or other waves due to the relative motion of the source and observer, taking into account the effects of special relativity. It uses the formula f_observed/f_emitted = ?((1 - ?)/(1 + ?)), where ? is the speed of the source as a fraction of the speed of light. This formula is crucial when determining the velocity of astronomical objects moving at speeds that are a significant fraction of the speed of light.

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