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प्रश्न
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उत्तर
The sound heard after reflection from a rigid obstacle is called an echo. To hear the cho of a sound distinctly, the reflecting surface in air should be at a minimum distance of 17 m from the listener.
If the distance is less than 17 m, the reflected sound will reach the ears before the original sound dies out. In such a case, the original sound mixes up with the reflected sound. Due to repeated reflections at the reflecting surface, the sound gets prolonged. This effect is known as reverberation.
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संबंधित प्रश्न
The displacement distance graph of two sound waves A and B, travelling in a medium, are as shown in the diagram below.
Study the two sound waves and compare their:
- Amplitudes
- Wavelengths
Explain how the principle of echo is used by
The dolphin to locate small fish as its prey
What are mechanical waves?
Mention two properties of a wave, one property which varies and the other which remains constant when the wave passes from one medium to another.
Why is an echo not heard when the distance between the source of sound and reflection body is less than 10 m?
(i) A man stands at a distance of 68 m from a cliff and fires a gun. After what time interval will he hear the echo, if the speed of sound in air is 340 ms−1?
(ii) If the man had been standing at a distance of 12 m from the cliff would he have heard a clear echo?
A sound wavelength of 0.332 m has a time period of 10−3 s. If the time period is decreased to 10−4 s, calculate the wavelength and frequency of the new wave.
Explain why, the ceilings of concert halls are curved.
