From reviewing previous posts on the subject, I understand that the E field and B field propagate in-phase through space. From this information, does it mean that at a specific space and time the E and B fields will be zero? If we had an instrument to determine the E and B field at specific times and locations, will there be measurements where both E and B-fields are equal to zero? To take it one step further, does this mean our measurement equipment will be sensitive to aliasing, and if we sample only when the E and B fields are zero there will be no EM wave detected (when the sampling rate is equal to the frequency of the wave being sampled)? Additionally, does the E and B-field amplitude matter when dealing with an interaction with a material? As a thought experiment, if we have a piece of matter that we send an em wave to, will there be a different interaction at the surface atoms if the interacting em wave has its E/B field at its max or at zero? I am trying to get a better understanding of electromagnetic waves, and thanks in advance for your responses. The following posts discuss how the E and F fields are in phase. https://www.physicsforums.com/archive/index.php/t-15160.html https://www.physicsforums.com/archive/index.php/t-36797.html PS (added at 09:16 AM): I just thought of another related question. I am not sure if this warrants a separate post. From the previous links, the electromagnetic wave is described as a self-propagating wave with its B-field and E-fields in phase. Does this mean that the E-field propagates the B-field that is 90 degrees further along the wave, which then also propagates the E-field 90 degrees along the wave? My logic being that if the B-field equals the differential of the E-field, when the slope of the E-field is max, the amplitude of the B-field is max at 90 degrees further along the wave.