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प्रश्न
How does a bat make use of ultrasonics waves to find its way?
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उत्तर
Use of ultrasonics by bats : Bats have no eyes. But they easily move about without colliding with any object (or obstacle). The reason is that they produce ultrasonic sound as they fly. When this ultrasonic sound comes back after reflection from any object (or obstacle) in their way, they hear it and thus they detect the presence of the object (or obstacle).
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संबंधित प्रश्न
Why are sound waves called mechanical waves?
Which one of the following does not consist of transverse waves?
Define the term wave velocity. Write its S.I. unit.
An observer X is on an island 5500 m from a vertical cliff on the shore. A ship Y is anchored between the island and the Cliff. A blast on the ship’s siren is heard twice by X, the interval being 5s. [Velocity of sound = 330 ms−1]
(i) Find the distance of the ship from the island.
(i) Find the distance of the cliff from the ship.
State the effect of pressure on the speed of sound in air.
Name the factors on which the speed of sound depends.
Define one hertz.
Match the following.
| Ultrasonics | Frequency below 20Hz |
| Speed of sound in air | Needs material medium |
| Infrasonics | 330ms-1 |
| Sound propagation | Frequency more than 20000 Hz |
Draw a curve showing density or pressure variations with respect to distance for a disturbance produced by sound. Mark the position of compression and rarefaction on this curve. Also, define wavelengths and time periods using this curve.
Assertion: The sound of thunder is heard a little later than the flash of light.
Reason: The speed of sound is much less than the speed of light.
