why all EM waves are sinusoidal ? or this is not true at all, i.e., EM waves of other waveforms do exist ? the above 2 questions are among the most vague in classical EM theory, of which i studied many topics in collage as an electrical engineering student, and i liked the subject so i kept reading about it in text books and over the internet, but unfortunately i still cannot find clear and convincing answers to them, iam not seeking a PURE mathematical answer, since what iam trying to understand is the logical link between pure mathematical equations and what really happens in the physical world. lets take the following example: if the excitation voltage applied to an antenna was of square waveform rather than sinusoidal, would this generate EM waves that can be detected by another antenna and then converted back to the original voltage waveform across some load connected to the receiving antenna ? and, most importantly; WHY ?