1. The three little bones in the middle ear are the _______, the anvil and the stirrup.   cochlea   hammer   eardrum   Hint Half-n-half Clue   2. The process by which sound vibrations are produced in pipes is known as _______.   reflection   rarefaction   resonance   refraction   Half-n-half Clue   3. A _______ note is the lowest note obtained on blowing gently across the top of a test-tube.   fundamental   overtone   harmonic   Half-n-half Clue   4. Ultrasonic vibrations are used in medicine for imaging internal organs of the human body.   True   False   5. If a flash of lightning is observed in a cloud 2970 m away and the speed of sound in air is 330 m/s, then the sound of thunder will be heard _______ s after the flash of lightning.   3   9   18   27   Half-n-half Clue   6. An airtight bell-jar is inverted on a platform connected to a vacuum pump. An electric bell fitted into the jar is operated but its sound cannot be heard. This is because sound cannot travel through _______.   glass   air   vacuum   Half-n-half Clue   7. The lower limit of frequency that can be heard by the average human is about   2 Hz   20 Hz   200 Hz   2000 Hz   Half-n-half Clue