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Class 11 Physics Practice Test: Waves - Doppler Effect
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The Doppler effect or Doppler shift is the apparent change in frequency of a wave in relation to an observer moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who described the phenomenon in 1842

Class 11 Physics Practice Test: Waves - Doppler Effect
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10 Questions

1. A passenger is standing on a platform. A train is arriving with speed =100m/s. It whistles at point B while the passenger is at point A. What is the frequency heard by the passenger if the whistle frequency is 100Hz? Speed of sound = 330m/s.
2. In case of electromagnetic waves, doppler shifts are independent of whether source moves or observer provided relative speed is the same. True or False?
3. A source of sound moves towards an observer. What happens to the speed of sound in the medium?
4. A source of frequency 50Hz is moving towards an observer with a deceleration of 2m/s2. If its initial speed is 20m/s, what will be the maximum frequency heard by the observer? Initial distance between source and observer is 100m. Speed of sound = 330m/s.
5. A source moves towards a stationary observer with a speed of 10m/s. If the frequency of the source is 10Hz what will be the wavelength of sound heard by the observer? Speed of sound = 330m/s.
6. A man is moving towards a wall with a source of sound in his hand. Frequency of source = 50Hz. Speed of man = 8m/s. If the man sends one pulse of sound, what will be the frequency heard by him after sound reflects off the wall? Speed of sound = 330m/s.
7. A man jumps from a building with a source of sound. When he reaches halfway down, he starts the siren of frequency 100Hz. A person standing below him on the ground hears the first sound to be of frequency 120Hz. What is the height of the building? Speed of sound = 330m/s. Take g=9.81m/s2.
8. An observer is standing stationary in air moving at a speed of 2m/s. A source of frequency 20Hz is moving in the direction of wind with speed 10m/s towards the observer. What will be the frequency as heard by the observer? Speed of sound in air is 330m/s.
9. If both the source of sound and observer are moving, the apparent frequency will be different from the actual frequency. True or False?
10. A train with a frequency ‘f’. What will be the frequency heard by a person sitting in the train? Speed of the train is ‘v’.