I've learned the Maxwell equations and how light is described as an electromagnetic field. But then the teacher just jumped to geometric optics.
I'm trying to understand light in terms of electromagnetic waves. How can something block a electromagnetic wave, like a mirror? Something my teacher told me is that, when the electromagnetic wave passes a metal, since the metal has free electrons, the electrons follow the changing electric field, producing a current and absorbing energy, so absorbing light. But how can you absorb electric field? The only thing I can think about is producing another field that counter-interacts with the original, thus canceling it, but how is it possible to the field produced happens to be exactly opposite to the original? Also, how can a dielectric material absorb light, if it does not free electrons?