Exam-style question
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What is the Doppler redshift?.
- A.A change in frequency due to the motion of a source relative to an observer
- B.A change in amplitude due to the motion of a source relative to an observer
- C.A change in wavelength due to the motion of an observer relative to a source
- D.A change in speed due to the motion of a source relative to an observer
Model answer
What a good answer should say
- A change in frequency due to the motion of a source relative to an observer
Explanation
Why this works
Doppler redshift refers to the change in frequency of waves from a source moving away from an observer, resulting in longer wavelengths. This effect applies when the source is receding, leading to a redshift in the observed light.
In contrast, other wave effects do not involve relative motion and do not result in a frequency change. Thus, Doppler redshift specifically indicates motion away from the observer.
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