Nature of Sound
Nature of Sound
Nature of sound : Sound is a mechanical and longitudinal wave. It needs material medium to propagate. It is produced by small and large pressure changes.
Speed of sound: Sound waves travel at different speeds in different substances. The speed of sound depends on various factors like temperature, nature and physical state of the substance, etc. for example, the speed of sound in air is about 3.30m/s at C and 346 m/s at room temperature. Also notice from table that sound waves travel fastest in solids and slowest in gases.
Substance | Speed (m/s) | Substance | Speed (m/s) |
Air | 346 | Aluminum | 5000 |
Water | 1498 | Iron | 5000 |
Mercury | 1452 | Diamond | 12,000 |
Glass | 5000 |
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Light, propagates faster than sound . All of us have, at one time or the other, been shaken and frightened by the roaring thunder sounds that follow flashes of lightning. The thundering sounds are always heard a little after seeing the flash of lightning. Why?
In early stages, people thought that we hear the thunder a little after seeing the lightning simply because the thunder perhaps occurred a little later. We now know that this is not the reason. Both lighting and thunder really occur together. The reason for the delay, in hearing the thunder, is due to the difference in the speeds of sound and light.
Measurement of the speed of light and sound tell us that light propagates very fast as compared to sound. The speed of sound in air is nearly 30 m/s (or 0.33 km per second) whereas speed of light is as high as 3 lakh kilometers per second. Light, thus, propagates nearly a million times faster than the sound. Hence, when lighting and thunder occur together, the flash of lighting (i.e. light) reaches us in practically zero time. The sound of the thunder however, takes a few seconds to reach us.
The frequency of a source 20 kHz. The frequencies of sound wave produced by it on water and air will be __________________ | |||
| Right Option : A | |||
| View Explanation | |||
The intensity of sound increase at night due to _____________________________ | |||
| Right Option : C | |||
| View Explanation | |||
A source of sound is moving a uniform speed along a cicle. the frequency of sound as heard by listener stationed at the centre of the path | |||
| Right Option : C | |||
| View Explanation | |||
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