Understanding Polarization: Exploring the Properties of Light

[Vanush]

Hi all.. I don't understand polarisation.

When unpolarised light is passed through a polarizer, the result is linearly polarised light with the E field oscillating in a direction parallel to the transmission axis of the polarizer. Say it passes through another sheet (analyzer) with its transmission axis at an angle theta to the transmission axis of the polarizer, then 'the component' of light parallel to the analyzer's transmission axis then let through.

What I don't get is.. Havent you already extracted a certain E-field direction from the light when you let it through the polarizer.. How can it have more components (which the analyzer 'extracts')??

Similarly, when linearly polarized light is passed through birefringent material, it still splits in two?? ie waveplate theory..

 

[merryjman]

You are right that the first polarizer has selected a direction for the light that passes through. But if the second polarizer is at an angle relative to the first, then the light's E-field direction will have both X- and Y- components when it reaches the second. I can call my vector (1,0) if I want, but if I rotate my frame of reference 90 degrees, now my vector is (0,1) isn't it? And in a third reference frame, this vector could be (0.7,0.7) couldn't it? Do you see the analogy?

Birefringent materials are more complicated, because they don't refract light in a linear isotropic fashion the way ordinary materials like glass and plastic do. In some directions light will refract a lot more than others. So for certain orientations of the birefringent crystal, you will have two beams - one that was refracted in the ordinary manner, and one that was refracted in the extraordinary manner.

 

[baba89]

Hi there,

Thank you for your question. Polarization is a property of light that describes the orientation of the electric field oscillations. When unpolarized light is passed through a polarizer, it becomes linearly polarized, meaning that the electric field oscillates in a single direction. The polarizer is able to filter out all other directions of the electric field, leaving only the desired direction.

When this linearly polarized light then passes through an analyzer, which is another polarizer with a different transmission axis, it can still be further filtered. This is because the analyzer only allows the component of the electric field that is parallel to its transmission axis to pass through. So, even though the light was already polarized by the first polarizer, the analyzer can still filter out certain directions of the electric field and let through the desired component.

In the case of birefringent materials, the light is split into two components with different polarization directions due to the material's properties. This is known as double refraction. These two components can then be manipulated by using a waveplate, which is a material with a specific thickness and orientation that can change the polarization of light passing through it.

I hope this helps to clarify the concept of polarization for you. Let me know if you have any further questions.