BRAINCAKEThe Doppler Effect and Red Shift
The Doppler effect is the change in the observed wavelength and frequency of a wave when its source moves relative to the observer. When the source moves away, the waves are stretched out: the observed wavelength increases and the frequency decreases. When the source moves towards the observer, the observed wavelength decreases.
For light from a galaxy moving away from us, the spectral lines are shifted towards the red end of the spectrum. This is called red shift. A galaxy moving towards us shows blue shift. The absorption lines keep the same pattern, so they can be recognised and compared with the wavelengths measured in a laboratory.
Sign in free to see the rest of this lesson, the R.E.C.I.P.E. recall steps and the quiz
BrainCake is free. Make an account in seconds and pick up where this page stops.
More in Astrophysics and Cosmology
- Estimating the Radius of a Star
- The Astronomical Unit, Light Year and Parsec
- Stellar Parallax
- The Cosmological Principle
- Hubble's Law
- The Big Bang Theory
- Cosmic Microwave Background Radiation
- The Age of the Universe
All 24 lessons in Astrophysics and Cosmology · All OCR A-level Physics topics