David Paraschuk : > Hello, > > I was just running though some of your excellent java applets and I have a question concerning the propagation of EM waves. Every text resource or web resource depicts the E and B field components as reaching a maximum and minimum in phase. Yet the theory of Maxwell clearly indicates that the rate of field change in the mutual self-induction cycle is what is important, ( E∝ £GB/£Gt ). I think during the wave cycle when the E field is a maximum, the rate of change temporarily falls to zero and the the B field at that instant would be zero. The opposite would be true for the generation of the E field by a changing B field. Therefore a maximum E and B field can never be produced together in time and space. > > If this follows then the traditional drawings of the EM waves are incorrect and the wave peaks should be out of phase by 180 degrees! > > If you could briefly comment on this thinking I would be in your debt. Thank you. It is the gradient of E in the space coordinate is proportion the rate of change in B field. i.e. grad E = - dB/dt It is different from E= -dB/dt (E and B should be out of phace) So E and B do not necessary to be out of phase. They can be in phase or out of phase or other case (phase different not 90 degree).