(c) of equal wavelength
   (d) of equal amplitude
Ans: (b)
310. Mica is used in an electric iron because it is a
   (a) good conductor of heat
   (b) good conductor of electricity
   (c) bad conductor of electricity
   (d) Both (a) and (b) above
Ans: (c)
311. Photo-electric cells convert
   (a) electrical energy into light energy
   (b) light energy into electrical energy
   (c) light energy into heat energy
   (d) electrical energy into heat energy
Ans: (b)
312. Lightning is produced when
   (a) similar charges of electricity rush towards each other and then get
   (b) clouds strike against impurities in air and the friction burns up these
   (c) strong opposite charges in different clouds break down the resistance
       offered by the intervening air
   (d) water vapour produces electricity in the clouds
Ans: (c)
313. The electrical domestic tube light gives white fiourescent light because of
   (a) collision between molecules of filled gas under electric current
   (b) heavy current
   (c) vacuum inside the tube
   (d) falling of ultra violet rays on the white inner coating of the tube
Ans: (d)
314. Choose the correct answer
   (a) Microphone converts sound energy into electrical energy.