Exam-style question
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Define Doppler redshift and explain how it differs from other wave effects such as frequency shift due to medium changes.
Model answer
What a good answer should say
- Doppler redshift refers to the increase in wavelength (or decrease in frequency) of light from an object moving away from an observer.
- In contrast, frequency shift due to medium changes occurs when waves travel through different media, affecting their speed and frequency without any relative motion between the source and observer.
- Doppler redshift applies in scenarios involving relative motion, such as stars moving away from Earth, while frequency shift due to medium changes applies in contexts like sound waves traveling through air and water.
Explanation
Why this works
This answer is strong because it clearly defines both concepts and identifies the key difference, which is the cause of the shift. It explains when each applies, providing context for the Doppler effect in astronomy and the medium effect in acoustics.
The conclusion reinforces the relevance of Doppler redshift in understanding cosmic phenomena.
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