A distant galaxy is observed at a distance of 125 Mpc125\text{ Mpc}125 Mpc from Earth. A hydrogen-beta spectral line, which has a rest wavelength of λ0=486.1 nm\lambda_0 = 486.1\text{ nm}λ0=486.1 nm, is detected in the light emitted by this galaxy.
Using a Hubble constant of H0=72 km s−1 Mpc−1H_0 = 72\text{ km s}^{-1}\text{ Mpc}^{-1}H0=72 km s−1 Mpc−1 and speed of light c=3.00×108 m s−1c = 3.00 \times 10^8\text{ m s}^{-1}c=3.00×108 m s−1, what is the observed wavelength of this spectral line on Earth?
472 nm472\text{ nm}472 nm
486 nm486\text{ nm}486 nm
488 nm488\text{ nm}488 nm
501 nm501\text{ nm}501 nm
53 exam-style questions on Edexcel GCSE Physics 7.2 The Universe and red-shift. Each one has a worked solution and a mark scheme showing where the marks go.