1. A _______ note is the lowest note obtained on blowing gently across the top of a test-tube.   fundamental   overtone   harmonic   Hint Half-n-half Clue   2. The approximate speed of sound in air is _______ m/s.   5000   1600   330   3 × 108   Half-n-half Clue   3. Sounds are produced by musical wind-instruments when columns of air are made to vibrate.   True   False   4. Out of the following materials, the best conductor of sound is _______.   Water   Steel   Air   Half-n-half Clue   5. The apparatus used in a ship to find out the depth of the sea underneath is called _______.   bell jar   tuning fork   sonar   Half-n-half Clue   6. When sounds reach the _______ or tympanic membrane, they make it vibrate.   hammer   eardrum   cochlea   Half-n-half Clue   7. If a flash of lightning is observed in a cloud 3300 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   10   20   30   Half-n-half Clue