A drone flies in a straight line at a constant speed. It carries a loudspeaker that emits a steady sound with a frequency of 720 Hz.
The speed of sound in air is 340 m/s.
The drone is flying towards microphone P and away from microphone Q. The table shows the frequencies recorded by these two fixed microphones.
| Microphone | Recorded frequency in Hz |
|---|---|
| P | 765 |
| Q | 680 |
Calculate the difference between the wavelength of the sound reaching microphone P and the wavelength of the sound reaching microphone Q.
A third microphone is fixed to the drone next to the loudspeaker.
Explain the frequencies recorded by the three microphones.
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.