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GCSE Physics · key term
An increase in the observed wavelengths of light from an object, shifting its spectral lines towards the red end of the spectrum.
Used by AQA, Edexcel and OCR
Paper 2
An increase in the observed wavelength of light compared with the wavelength at which it was emitted.
Revise: Red-shiftWhen astronomers compare light from a distant galaxy with light of known wavelengths, they find that recognisable features in its spectrum are often shifted towards longer wavelengths. This increase in observed wavelength is red-shift. It does not mean that every part of the light has become visibly red.
Specification 7.9P, 7.10P, 7.12P, 7.13P, 7.14P · Paper 1
Describe red-shift as an increase in observed wavelength, not simply as light becoming red.
Link each observation to the conclusion it supports: red-shift indicates expansion; the CMB is evidence of a hot early Universe.
When asked why the Big Bang theory is accepted, compare the evidence: red-shift is consistent with both an expanding Big Bang universe and the Steady State model, whereas the cosmic microwave background strongly supports the Big Bang model and is not satisfactorily explained by Steady State.
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An increase in the wavelength of light received from a distant galaxy, shifting its spectral lines towards the red end of the spectrum.
Two important observations are red-shift and cosmic microwave background radiation.
The displacement of features in light from a distant galaxy towards longer, redder wavelengths, indicating that the galaxy is moving away.
The displacement of identifiable lines in a spectrum towards longer wavelengths.
An increase in the observed wavelengths of light, shown by spectral lines moving towards the red end of the spectrum compared with their known positions.
An increase in the observed wavelength of light, with its spectral lines displaced towards the red end of the visible spectrum.
Specification P8.3a, P8.3b · Paper 2 (Foundation), Paper 4 (Higher)
An increase in the observed wavelength of light from a receding object, accompanied by a decrease in its frequency.
Revise: Red-shiftIf a galaxy is moving away from us, the light waves we receive are stretched to longer wavelengths and therefore lower frequencies. Its familiar spectral-line pattern is shifted towards the red end of the visible spectrum. This is called red-shift.
An increase in the wavelength of light received from an object moving away from us.
Paper 1, Paper 2
Revise: Red-shift and Evidence for the Big BangA shift of the galaxy's spectral lines towards longer wavelengths is therefore called red-shift. It indicates that the galaxy is receding from us. A source approaching an observer would instead have shorter observed wavelengths and a blue-shift.