Problems from Fishbane, Gasiorowicz, and Thornton
(2nd edition) Chapter 35

22.  A radio station emits a signal with a power of
     30 kW.  What are the peak values of the electric
     field and magnetic field at distances of 5 km and
     100 km?  Assume that the signal far from the 
     antenna is transmitted with equal intensity in
     all directions.  (Real radio stations cannot
     afford to transmit their energy in this way, and
     their antennas distribute energy with a high
     degree of directionality.)

32.  A 100 W lightbulb radiates uniformly in all
     directions, and 7 percent of this energy is 
     emitted as electromagnetic radiation in the
     visible light range.  What is the electromagnetic
     energy density of visible light at a distance of
     80 cm from the bulb?  What are the rms values of
     the corresponding electric and magnetic fields
     there?