IB Physics HL C 5 4 Spectral Line Shifts Questions
Interpret spectral red-shift and blue-shift as evidence of relative motion and cosmic expansion, and use Hubble law to calculate distances.
- Syllabus
- First assessment 2025
- Course
- Physics HL
- Level
- HL
Exam points
- define red-shift and blue-shift by comparing observed spectral-line wavelength with the laboratory or rest wavelength
- calculate recessional or approach velocity and galaxy distance from spectral-line shifts, Hubble law and the Hubble constant
- explain how systematic galaxy red-shifts, spectral observations and changing cosmic scale factor support an expanding universe
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IB Physics HL C 5 4 Spectral Line Shifts Questions question 1
[Maximum number: 2]
A beam of coherent monochromatic light from a distant galaxy is used in an optics experiment on Earth.
The wavelength of the light in the beam when emitted by the galaxy was 621.4 nm .
Explain, without further calculation, what can be deduced about the relative motion of the galaxy and the Earth.
wavelength increases (so frequency decreases) / light is redshifted;
galaxy is moving away from Earth
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