Humans can sense the polarization of light with the naked eye
I've never understand the idea that in non-polarized light, the "amplitude" of the light wave points in all directions, whereas in polarized light it points in only one. The amplitude of a light wave doesn't literally mean something is oscillating up and down, right?? The amplitude is just the light's intensity. So what does it really mean for light to be polarized? And why do thin slits cause polarization?