Question 21
FA car is moving to the right at a constant speed. Its horn makes a sound of constant frequency.
Observer P stands in front of the car. Observer Q stands behind the car.
The Figure shows the wavefronts of the sound from the horn.
Figure
a.[1]
Use the Figure to compare the wavelength of the sound reaching observer P with the wavelength of the sound reaching observer Q.
b.[1]
State how the frequency heard by observer P compares with the frequency of the sound made by the horn.
c.[2]
Explain why observer Q hears a lower frequency than the frequency of the sound made by the horn.
d.[1]
The car stops. The horn keeps sounding at the same frequency.
State the frequency now heard by observer P.
7.2 The Universe and red-shift Questions
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.