1. The approximate speed of sound in air is _______ m/s.   1600   330   5000   3 × 108   Hint Half-n-half Clue   2. Sounds travels faster in air as compared to water.   True   False   3. The process by which sound vibrations are produced in pipes is known as _______.   reflection   resonance   rarefaction   refraction   Half-n-half Clue   4. The repetition of sound which is reflected from an object is referred to as _______.   an echo   the amplitude   the pitch   Half-n-half Clue   5. Ultrasonic vibrations are used in medicine for imaging internal organs of the human body.   True   False   6. The sound of thunder is heard 6 s after the flash of lightning. If the speed of sound in air is 330 m/s, then the cloud is at a distance of _______.   55.0 m   110.0 m   990 m   1980 m   Half-n-half Clue   7. Out of the following materials, the best conductor of sound is _______.   Air   Water   Steel   Half-n-half Clue