Energy in the Electromagnetic Field. 25 



the energy current at any point. But we have still to seek 

 an explanation as to how a flow of energy in the manner 

 described above leads to the actual distribution of maxima 



Fig. 5. 



Illustrating the form of the lines of flow of energy in different parts of 

 the field. The thin lines are the "mean lines of flow" and the 

 heavy lines the actual lines of flow. 



and minima of illumination in the field. The current of 

 energy at an)- point is by (19) 



B-^(l-8«oo.^^ + ^), 



