Hi all, To me, polarization is the most confusing concepts in optics to me. From the text, it is said that polarization is how the light oriented. A linear polarization means the light is oriented on one direction. But I have few doubts I learn from the book and online materials 1) In most book and some youtube material, it is said that a linear polarizer is used so an unpolarized light only have one orientation of the light can pass through. My understanding is an unpolarized light has components of all direction. Even some components is not along the transmission direction of the polarizer, but those components could have some projection along the transmission direction. So basically, all components oriented at any direction could pass the liinear polarizer but some direction will all go through some will just a bit, depends on the projection. Is that correct? 2) In wiki (https://en.wikipedia.org/wiki/Linear_polarization), it explains the linear polarization as linear-polarized along a plane consisting of two orthogonal, in-phase components. My first question is why there will be two components of the electric field? I know electric field component is a vector so it could decomposed into any two components, is this the reasoning why there are two components? If so, can I say linear polarized light is the electic field oriented a specific direction which doesn't not change in time so the decomposed two components are always in-phase? 3) I read a video in youtube about circular polarization. The guy explain that a circular polarization means two components of the electric fields are not moving at the same speed, one is lag by 1/4 wavelength than the other, so the tip of the synthesized electric field vector is along a helix. If we view from the direction of propagation, we see a circle. Am I understand this correctly? 4) I remember I read it somewhere about circular polarized light reflected by a mirror, will the direction of circular polarization opposite if we use a mirror to reflect the light in circular polarization? For example, if we have a clockwise circular polarized light inject into a mirror making 30 degree to the light, will the reflected light becomes counterclockwise circular polarized? why? 5) the last question is about how to check the circular polarization in experiment. I read this online, someone use a quarter-wave plate and a beam splitter cube. Passing the circular polarized light to the quarter-wave plate and left the outgoing light through the beam splitter, the component perpendicular to the direction of propagation should be zero if the incoming light is circular polarized, why is that? Sorry for the long question. I am trying to collect as much information as I can to understand the light polarization, I just want to confirm with someone here that my understanding is correct or not.