An ambulance siren emits a sound of frequency 1800 Hz. The speed of sound in air is 330 m/s. The ambulance moves towards a stationary observer at a constant speed of 50 m/s. What is the frequency heard by the observer?
Correct answer: C. (1800 * 330) / 280
- A. (1800 * 290)/ 330
- B. (1800 * 330) / 370
- C. (1800 * 330) / 280
- D. (1800 * 330) / 380
Explanation
Doppler's formula fo=v+vo/v+vs x fs fo= 330x1800/330-50 fo=330x1800/280
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About Speed of Sound
The speed of sound depends on the properties of the medium, including its elasticity and density, and in gases it varies mainly with temperature. Questions connect speed with frequency and wavelength, compare sound in solids, liquids and gases, and distinguish the speed of propagation from the oscillating particles' motion.
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