Sound

No. Sound       
1. To calculate the depth of the seas and oceans reflection of sound is used.
2. To hear the sound from source and after reflection separately the man should stand atleast 11 metres or more from the reflecting surface.
3. To avoid echoes bad reflectors of sound are used to cover the walls of auditoria, cinema halls etc.
4. Thermocol, Porus material etc., are the bad reflectors of sound.
5. Plawood, Metal sheets, walls etc. are good reflectors of sound.
6. Sound follows all the laws of reflection of light.
7. Two sounds can be heared separately if the gap between the sounds is atleast 1/15 of a second.
8. The sound can reflect as light. The reflected sound is called echo.
9. Sound travels in solids faster than in liquids.
10. Sound travels in glass with a speed of 5500 metres per second.
11. Sound travels in water with a speed of 1435 metres per second.
12. Sound travels in air with a speed of 330 metres per second.
13. One sound wave constitute one compression and one rarefaction.
14. Sound can travel in gases. Every vibration has one compression and one rarefaction.
15. Sound does not travel in vacuum. A medium is essential for its propagation from one place to another.
16. Number of vibrations of an object per second is called frequency.
17. Motions of bodies to produce sound are called Vibrations.