(d) It will make the temperature go up and down
Ans: (b)
67.Decibel is the unit of physical quantity used for: [SSC Graduate 2005]
   (a) the speed of light
   (b) the intensity of heat
   (c) the intensity of sound
   (d) the frequency of radiowaves
Ans: (c)
68.The echo is produced by the sound waves due to : [RRB Driver 2002]
   (a) the reflection of sound
   (b) the scattering of sound
   (c) the refraction of sound
   (d) None of these
Ans: (a)
69.SONAR is frequently used by : [UPPCS (Pre) 2004]
   (a) Astronauts
   (b) Doctors
   (c) Engineers
   (d) Navigators
Ans: (d)
70.The pitch or frequency of the siren of a coming train appears to be increasing
   because of : [RRB ASM/GG 2005]
   (a) Big-bang theory
   (b) Doppler"s effect
   (c) Charle"s law
   (d) Archemedes"s principle
Ans: (b)
71.The normal temperature of the human body is : [IAS (Pre) 1995]
   (a) 280 K
   (b) 290 K
   (c) 300 K
   (d) 310 K
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