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GCSE Physics · key term
A huge collection of stars, gas and dust held together by gravity.
Used by OCR
Specification P8.3a · Paper 2 (Foundation), Paper 4 (Higher)
Revise: Red-shiftA galaxy contains many stars, and their light travels across space to reach us. Light is a wave. Its wavelength is the distance from one wave crest to the next; its frequency is the number of waves passing a point each second.
This OCR learning outcome is Higher Tier and qualitative: describe the changes in wavelength and frequency without calculating a galaxy’s speed.
Red-shift does not mean a galaxy simply looks red. Identify the shift by comparing the positions of its spectral lines with their expected positions.
State the distance trend precisely: more distant galaxies generally recede faster.
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