Thank you. I was being bombarded by textbook with information. Your video gave me a clearer picture 👍👍

Thank you very much for the video! It was very clear and helpful. I was slightly confused by one small point though, and I would appreciate it if you could clarify it: From 4:00 - 4:13: "But because we have different speeds of light travelling through the material based on the different polarisations, we're going to cause that shift like we saw before." So to be clear, the shift is the result of different polarisations having seemingly different indices of refraction. Here is where my misunderstanding lies: at around 4:39, you add a birefringent material in between two orthogonal polarisers. The light incident to the material will be polarised in one specific direction only. So how will the subsequent phase shift arise? (4:38 - 4:42, "but if we start adding the material back again, then we can start getting a phase shift..."). I thought that the shift only arises if you have two different polarisations that will travel at different speeds though the material resulting in the phase shift you described. What am I missing here?

I've seen several sources that say that light at normal incidence to a birefringent material still has one of the polarizations changing angle, instead of having the light go straight through, and Snell's law doesn't hold for birefringent materials. There are also videos on youtube showing a laser at normal incidence to a birefringent crystal, and the direction of one of the polarizations actually changes when the crystal is rotated, while keeping the angle of incidence at 0. I also thought that birefringent materials just had two indices of refraction, where on depends on the orientation of the crystal (and makes an ellipsoid shape), but apparently Snell's law no longer holds at the interface for the extraordinary ray. I'm wondering if there's some more general version that does.

At pi/2 wavelength from your starting point the intensity of light is 0,since both light waves at said given point have 0 intensity.Also to generate circularly polarized light don't we need a phase difference of pi/2?When you say shifting do you mean shifting the orthogonal wave?

Hello, thank you for enriching the KZfaq community with your videos! To make sure no misinformation is spread, I wanted to bring up a seeming contradiction with other sources and get your input. In your example on normal incidence, I have understood you to mean that both the ordinary and extraordinary ray will propagate at angle 0. However, two sources I've been reviewing so far explain that the extraordinary beam in birefringent materials will not (except under specific conditions) propagate at a zero angle under normal incidence. What do? Seemingly conflicting sources: Wikipedia: en.wikipedia.org/wiki/Birefringence#Double_refraction "So even in the case of normal incidence, where the angle of refraction is zero (according to Snell's law, regardless of effective index of refraction), the energy of the extraordinary ray may be propagated at an angle." Another KZfaq Video: kzfaq.info/get/bejne/oMumhrKop9rVnH0.html#t=4m03s

4:15 I don't see the two polarizers...