(b) these are not electromagnetic in nature
   (c) their wavelength is very large
   (d) they are not reflected by the ionosphere but pass through it
Ans: (d)
128. Heat transfer
   (a) cools the body that transfers it
   (b) heats the body that absorbs the heat
   (c) may change the physical state of the substance
   (d) All the above
Ans: (d)
129. The presence of impurities
   (a) lowers the melting point of ice
   (b) raises the melting point of ice
   (c) has no effect on the melting point of ice
   (d) may lower or raise the melting point depending upon the type of
Ans: (a)
130. In a freezer ice cubes will be formed more quickly in trays made of
   (a) rubber
   (b) plastic
   (c) aluminium
   (d) wood
Ans: (c)
131. Water kept in an earthen pot is less cool on rainy days than in summer
   because during the rainy days
   (a) the pores in the pot are closed
   (b) rain water stops oozing out from the pores
   (c) the water that oozes out does not evaporate quickly because of the large
       percentage of moisture in the air
   (d) surface of the pot becomes damp
Ans: (c)