a)  What is the amount of energy supplied to the lamp each second in joules?

         b)  What is the amount of energy transferred usefully as light each second in joules?

         c)  What is the amount of energy wasted each second in joules?

         d)  What is the efficiency of the lamp?

    2.  The following diagram is about a radio.

         a)  What is the useful energy?

         b)  What is the wasted energy?

         c)  What is the efficiency of the radio?

    3.  In a solar cell, for every 100 J of solar energy shining on it, only 5 J is transferred to useful

         energy (as electricity).

         a) What happens to the other 95 J?

         b) What is the efficiency of the solar cell?

         c) Why are solar cells not yet in widespread use?