# I How is Circularly polarized light changed upon refraction?

1. Jun 14, 2016

### 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?

2. Jun 15, 2016

### Twigg

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.

3. Jun 15, 2016

### Latempe

Ah thank you! This helps my understanding a lot!