# How is Circularly polarized light changed upon refraction?

• Latempe
In summary, when polarized light is incident on a surface, it can change handedness and remain circular if it is at an angle less than the Brewster angle. However, the transmitted wave will not change handedness and will remain circular at normal incidence. At general incidence, the transmitted wave will have an elliptical polarization state. This is due to the fact that the transmitted wave amplitude coefficients are always positive values in the Fresnel equations, unlike the reflected wave.
Latempe
I have a pretty good understanding that when polarized light is incident on a surface it will change handedness (Right handed polarization, to left handed polarization for example) and remains will remain circular if it is incident at an angle less than the Brewster angle, otherwise it will retain its handedness but become elliptically polarized.

But what happens to the transmitted wave? How does it's handedness change? Can it ever remain circular? What happens at normal incidence?

Recall that in the Fresnel equations the numerators for the transmitted wave amplitude coefficients are always positive values, unlike the reflected amplitude coefficients. That means you don't get flipping, like with the reflected wave. The transmitted wave remains circular at normal incidence, since ##t_{\parallel}|_{\theta_{i} = 0} = t_{\perp} | _{\theta _ {i} = 0 } = \frac{2n_{i}}{n_{i}+n_{t}}##. At general incidence, ##\frac{t_{\perp}}{t_{\parallel}} = \frac{n_{i} \cos \theta_{t} + n_{t} \cos \theta_{i}}{n_{i} \cos \theta_{i} + n_{t} \cos \theta_{t}}##, so you should get some kind of elliptical polarization state in general.

Latempe
Ah thank you! This helps my understanding a lot!

## 1. What is circularly polarized light?

Circularly polarized light is a type of electromagnetic radiation that has equal components of electric and magnetic fields, with the electric field rotating in a circular motion.

## 2. How is circularly polarized light different from linearly polarized light?

Circularly polarized light has a continuously changing direction of polarization, while linearly polarized light has a fixed direction of polarization.

## 3. How is circularly polarized light changed upon refraction?

When circularly polarized light enters a medium with a different refractive index, its direction of rotation may change, but it will still remain circularly polarized.

## 4. Can circularly polarized light become linearly polarized upon refraction?

Yes, if the medium has a preferential direction of polarization, circularly polarized light can become linearly polarized upon refraction.

## 5. What is the relationship between circularly polarized light and handedness?

Circularly polarized light is said to have a handedness, either left-handed or right-handed, depending on the direction of its electric field rotation. This is analogous to the concept of chirality in chemistry.

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