Questions
Question 1
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What happens to the observed frequency of light when source and observer approach each other?
Question 2
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What happens to the observed wavelength of light from a receding source?
Question 3
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State the longitudinal relativistic Doppler formula for an approaching source.
Question 4
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State the longitudinal relativistic Doppler formula for a receding source.
Question 5
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A source emits \(5.00\times10^{14}\,\mathrm{Hz}\) and approaches slowly enough that the observed frequency is \(6.00\times10^{14}\,\mathrm{Hz}\). Is this a redshift or blueshift?
Question 6
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A spectral line has rest wavelength \(500\,\mathrm{nm}\) and observed wavelength \(550\,\mathrm{nm}\). Find the redshift \(z\).
Question 7
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A source emitting \(5.00\times10^{14}\,\mathrm{Hz}\) approaches at \(0.200c\). Find the observed frequency.
Question 8
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A source emitting \(6.00\times10^{14}\,\mathrm{Hz}\) recedes at \(0.200c\). Find the observed frequency.
Question 9
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A rest wavelength \(500\,\mathrm{nm}\) is observed at \(650\,\mathrm{nm}\). Find \(z\) and state whether the source is approaching or receding.
Question 10
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A source recedes at \(0.600c\). By what factor is the observed frequency changed?
Question 11
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A source approaches at \(0.600c\). By what factor is the observed wavelength changed?
Question 12
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A galaxy has redshift \(z=0.500\). What is the ratio \(\lambda_o/\lambda_s\)?
Question 13
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For a receding source, derive \(\lambda_o/\lambda_s=\sqrt{(1+\beta)/(1-\beta)}\).
Question 14
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A source has observed wavelength twice its rest wavelength. Find the recession speed.
Question 15
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A source emits at \(400\,\mathrm{nm}\) and approaches at \(0.800c\). Find the observed wavelength.
Question 16
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Derive the source speed in terms of the wavelength ratio \(R=\lambda_o/\lambda_s\) for a receding source.
Question 17
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Why is the relativistic Doppler effect for light symmetric between source motion and observer motion?
Question 18
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Show that the approaching and receding Doppler factors are reciprocals.
Question 19
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Explain why using the sound Doppler formula for light in vacuum is conceptually wrong.
Question 20
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Show that the receding relativistic Doppler formula becomes the approximate low-speed redshift \(z\approx\beta\).