Doppler effect

The data below was obtained during an investigation into the relationship between the different velocities of a moving sound source and the frequencies detected by a stationary listener for each velocity. The effect of wind was ignored in this investigation.


1.Write down the dependent variable for this investigation.(1)

2.State the Doppler effect in words. (2)

3.Was the sound source moving TOWARDS or AWAY FROM the listener? Give a reason for the answer. (2)

4.Use the information in the table to calculate the speed of sound during the investigation. (5)

5. The spectral lines of a distant star are shifted towards the longer wavelengths of light. Is the star moving TOWARDS or AWAY FROM the Earth? (1) [11]


The Doppler effect is applicable to both sound and light waves. It also has very important applications in our everyday lives.A hooter on a stationary train emits sound with a frequency of 520 Hz, as detected by a person standing on the platform. Assume that the speed of sound is 340 m∙s-1 in still air.

1. Calculate the:

1.1 Wavelength of the sound detected by the person (2)

1.2 Wavelength of the sound detected by the person when the train moves towards him/her at a constant speed of 15 m∙s-1 with the hooter still emitting sound (6)

2.Explain why the wavelength calculated in QUESTION 6.1.1 differs from that obtained in QUESTION 1.2. (2)

3. Use your knowledge of the Doppler effect to explain red shifts (2) [12]




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