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प्रश्न
Why do we hear more clearly in a room with curtains than in a room without curtains ?
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उत्तर
We hear more clearly in a room that is curtained than in a room that is uncurtained because curtains are bad reflectors of sound. They absorb most of the sound falling on them, and hence do not produce echoes. On the other hand, in an uncurtained room, there is a greater reflection of sound and thus echoes are formed. These echoes cause a hindrance to hearing. Therefore, we hear more clearly in a room with curtains than in a room without curtains.
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संबंधित प्रश्न
Explain why, the flash of lightning reaches us first and the sound of thunder is heard a little later.
Name three devices which work on the reflection of sound.
What is the other name of a loud-hailer ?
Fill in the blank with suitable word :
Echoes are caused by the ...................... of sound.
What is the minimum distance in air required from a sound reflecting surface to hear an echo (at 20°C) ?
A man standing 825 metres away from a cliff (steep rock) fires a gun. After how long will he hear its echo ? Speed of sound in air is 330 m/s.
An echo-sounder in a trawler (fishing boat) receives an echo from a shoal of fish 0.4 s after it was sent. If the speed of sound in water is 1500 m/s, how deep is the shoal ?
Assertion: The sound which we hear again is called Echo.
Reason: The sensation of sound (Echo) persists in our brain for about 1 s.
Numerical problems:
An echo returned in 3s. What is the distance of the reflecting surface from the source given that the speed of sound is 330 ms-1?
Answer the following question in your own words.
What factors are important to get a distinct echo?
