C.5 Doppler effect Quiz
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5 questions, one answer each
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1. A star's spectral lines are all shifted to longer wavelengths. The star is:
- A. Moving towards us
- B. Moving away from us
- C. Getting hotter
- D. Getting closer to its companion
2. A line at 500.0 nm is observed at 500.5 nm. What is the speed of the source?
- A. 3.0 × 10⁵ m s⁻¹
- B. 3.0 × 10⁶ m s⁻¹
- C. 1.5 × 10⁵ m s⁻¹
- D. 3.0 × 10⁸ m s⁻¹
3. Behind a moving source of sound, the wavefronts are:
- A. Closer together
- B. Further apart
- C. Moving faster
- D. Unchanged
4. An observer moves towards a stationary sound source. Which quantity at the observer is unchanged?
- A. Frequency heard
- B. Wavelength
- C. Rate of arrival of wavefronts
- D. Pitch
5. When is Δλ/λ ≈ v/c valid?
- A. Only for sound
- B. When v is much smaller than c
- C. When v is close to c
- D. Only for moving observers