Two identical sound sources emit the same frequency. Source P moves towards a stationary observer and source Q moves away at the same speed. The air is still.
Which correctly compares the waves reaching the observer?
P has a longer wavelength; both waves travel at the same speed.
P has a shorter wavelength; both waves travel at the same speed.
P has a longer wavelength; its waves travel at a greater speed.
P has a shorter wavelength; its waves travel at a greater speed.
94 exam-style questions on Edexcel GCSE Physics 7.2 The Universe and red-shift, covering 7.2.1 Big Bang and Steady State theories, 7.2.2 Evidence for the Big Bang, 7.2.3 The Doppler effect and red-shift, 7.2.4 Red-shift as evidence for an expanding Universe, and 7.2.5 The CMB and the accepted model. Each one has a worked solution and a mark scheme showing where the marks go.