(c) the electric bell
   (d) All the above
Ans: (d)
240. The Cact that the compass needle does not point true north was observed
   first by
   (a) Sir Isaac Newton
   (b) Columbus
   (c) Archimedes
   (d) Thomas Alva Edison
Ans: (b)
241. The loudness of a sound is determined by
   (a) Frequency
   (b) Amplitude
   (c) Speed
   (d) Wavelength
Ans: (b)
242. A person cups his hand around the mouth when shouting. Why?
   (a) Sound energy from his mouth is then directed in one direction
   (b) The cupped hand acts as a cardboard tube of short length
   (c) The pitch of sound increases
   (d) Both (a) and (b)
Ans: (d)
243. If a man wants to hear clearly the echo of a sound produced by him from
   a hill, the hill should be away from him by a minimum distance of
   (a) 330 m
   (b) 33 m
   (c) 16.5 m
   (d) 165 m
Ans: (c)
244. If a band is played on the moon the sound will
   (a) reverberate
   (b) be heard by us faintly