SP7d Red-shift | Edexcel GCSE Physics Separate Science Topic Mastery Pack

A focused three-component revision and exam practice pack for SP7d, covering the complete Edexcel Separate Science Physics specification for the Doppler effect and the red-shift of galaxies (P7.11P–P7.13P).

Topic Mastery Sheet covers the Doppler effect for sound - compression and stretching of waves from a moving source - as the concrete foundation before applying the same principle to light. It explains how spectral dark lines (produced by element absorption) are used to detect red-shift in galaxy spectra, and presents the relationship between red-shift magnitude and galaxy distance that Hubble established. The conclusion - that all distant galaxies are receding and the Universe is therefore expanding - is developed from the evidence rather than stated as a given. A common misconception is addressed: red-shift does not mean galaxies are moving through space away from us, but that space itself is expanding and carrying them with it.

Student Exam Practice Sheet includes a three-part Doppler question on a police siren (naming the effect, describing the pitch change, explaining in terms of wavelength); a four-part red-shift question including an MCQ on the definition, a recession-direction question, and two data-interpretation questions using a relative red-shift table; and a two-mark question on what red-shift tells us about the Universe. Question format matches the Edexcel end-of-unit test style.

Teacher Answer Key provides a complete mark scheme with examiner notes specifying that the Doppler explanation requires both compression/stretching of waves and the resulting frequency change for full marks, and that “the Universe is expanding” requires the prior point that galaxies are moving away for both marks on Q3.

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