Sound (Practice Sheet, Class 9)

(1) Give an example to prove that sound can travel in water.

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(2) Write two characteristics of the sound.

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(3) A sound wave has a frequency of 20 Hz and wavelength 20 cm. How long will it take to travel 1 km.

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(4) Why megaphone is used to make announcement.

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(5)How ultrasonic waves are useful in ‘echocardiology’?

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(6) A ship sends out ultrasound that returns from the seabed and is detected after 2 s. If the speed of ultrasound through seawater is 1200 m/s, what is the distance of the seabed from the ship?

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(7) Write the difference between the infrasound and ultrasound.

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(8) A echo is heard in 2 s. What is the distance of the reflecting surface from the source, given that the speed of sound is 342 m/s.

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(9) Write the name of three bones which amplified vibrations several times in the middle ear.

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(10) What is the minimum time interval between the original sound and the reflected one to hear echo?

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Helping Topics

Sound

NCERT solutions, class 9

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