Question

Answer the question 6 and 7 ...

Plz don't copy paste from google.Give your own answer and don't give unwanted answer.
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Answer 1

Answer:

6 ) Sound needs a material medium for their propagation like solid, liquid or gas to travel because the molecules of solid, liquid and gases carry sound waves from one point to another. Sound cannot progress through the vacuum because the vacuum has no molecules which can vibrate and carry the sound waves.

7 ) A. 20 Hz - 20,000 Hz

    B. Sound waves with frequencies less than 20Hz are called infrasonic or subsonic and those with frequencies above 20kHz are called ultrasonic. ... They do this by "speaking" and hearing with infrasonic waves which we cannot hear but can bend around obstacles rather than being absorbed like normal sound.

Answer 2

Answer:

yBtH........................