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Name the following.
The cell organelle which synthesizes protein.
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Explain why, the flash of lightning reaches us first and the sound of thunder is heard a little later.
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Which of the following statement best describes frequency?
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Which property of sound leads of the formation of echoes ?
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Name three devices which work on the reflection of sound.
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What is the other name of a loud-hailer ?
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Name the device which is used to address a small gathering of people.
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Fill in the blank with suitable word :
An echo is simply a ................... sound.
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Fill in the blank with suitable word :
Echoes are caused by the ...................... of sound.
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On which day, a hot day or a cold day, an echo is heard sooner ? Give reason for your answer.
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In which medium, air or water, an echo is heard much sooner ? Why ?
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Why do we hear more clearly in a room with curtains than in a room without curtains ?
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Why are the ceilings of concert halls made curved ? Draw a labelled diagram to illustrate your answer.
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The echo of a sound is heard after 5 seconds. If the speed of sound in air be 342 m/s, calculate the distance of the reflecting surface.
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The speed of sound in water is 1500 metres per second. How far away from an under-sea rock should a deep sea diver be so that he can hear his own echo ?
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What is meant by 'reflection of sound' ? What type of surfaces are the best for reflecting sound ?
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Name any two objects which are good reflectors of sound.
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State the laws of reflection of sound.
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What is an echo ? How is echo formed ?
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What is the minimum distance in air required from a sound reflecting surface to hear an echo (at 20°C) ?
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