1. Sound can be reflected as well as refracted.   True   False   2. Ultrasonic vibrations are used in medicine for imaging internal organs of the human body.   True   False   3. Echoes are caused by _______ of sound.   reflection   refraction   rarefaction   Hint Half-n-half Clue   4. Dolphins use infrasonic vibrations to locate objects and their prey.   True   False   5. An echo from the sea-bed is received 1.50 s after an ultrasonic vibration is sent from a sonar on a ship. If the speed of sound in water is 1500 m/s, then the depth of the sea is _______.   1000 m   1125 m   2250 m   4500 m   Half-n-half Clue   6. The approximate speed of sound in air is _______ m/s.   5000   1600   330   3 × 108   Half-n-half Clue   7. The process by which sound vibrations are produced in pipes is known as _______.   refraction   reflection   rarefaction   resonance   Half-n-half Clue