(d) cosmic rays coming from space
Ans: (b)
123. The plants in a greenhouse are enclosed in a glass enclosure because
   (a) glass allows the heat radiations of shorter wavelengths from the sun to
       pass through
   (b) the plants absorb them - these shorter wavelengths - and reradiate them in
       the form of longer wavelengths
   (c) the longer wavelengths cannot penetrate through the glass walls
   (d) All the above
Ans: (d)
124. The cover of a solar cooker is made of glass because
   (a) it absorbs sun"s rays
   (b) it reflects sun"s rays
   (c) it retains the heat inside by the greenhouse effect
   (d) it radiates heat better than metals
Ans: (c)
125. The inside of both the walls of a thermos flask is silvered i.e., on the
   vacuum side in order to reduce heat loss by
   (a) convection
   (b) radiation
   (c) conduction
   (d) All the three
Ans: (b)
126. When ice just melts
   (a) there is no change in volume
   (b) there is no change in temperature
   (c) heat is given out
   (d) there is no change of state
Ans: (b)
127. Before the invention of geostationary satellites, television stations could
   not transmit their programmes to far off places because
   (a) these signals are electromagnetic in nature