147. Radio waves sent out by radio stations are reflected by
   (a) troposphere
   (b) stratosphere
   (c) mesosphere
   (d) ionosphere
Ans: (d)
148. The maximum range of most TV signals is from 121 to 240 km only
   because
   (a) the curvature of earth limits the range of reception
   (b) the signals are weak
   (c) the signals are absorbed by air
   (d) the antennae are not powerful enough
Ans: (a)
149. Less dew is formed on cloudy nights because
   (a) there is no moisture in the atmosphere
   (b) clouds absorb the falling dew
   (c) objects emit radiant energy very fast on such nights
   (d) objects lose less radiant energy
Ans: (d)
150. In a refrigerator cooling is produced by
   (a) the ice that deposits on the freezer
   (b) the evaporation of a volatile liquid
   (c) None of the above
   (d) Both (a) and (b)
Ans: (b)
151. The base of an electric iron is brightly polished mainly
   (a) to make it smooth and frictionless
   (b) to make it rust - proof
   (c) to reduce heat loss by radiation
   (d) to make it more durable
Ans: (c)
152. Match the following:
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