# Things to talk about in a Polarization Write-up

authoriseddiplidocus

## Homework Statement

I am doing an assignment on Polarization of light. I have conducted experiments to prove that reflected light is at least partially plane-polarized, and to prove that Malus' Law is true. Both my experiments have given good results. I now need to find enough stuff to write about polarization that the marker doesn't think all I've done is got some data.

## Homework Equations

Can someone briefly explain or post a link to tell me how Malus' Law actually works? Why is the equation as it is? What is the physics behind it?
Why is reflected light plane-polarized?
Which component/vector of an EM wave (Electric or magnetic) does a polarizing filter eliminate and why?

## The Attempt at a Solution

Currently, I've explained how an EM wave is made up of perpendicular electric and magnetic field vectors oscilating perpendicular to each other and perpendicular to the direction of propagation. I've also explained that natural/un-polarized light has these vectors oscillating in all planes, whilst plane-polarized light has eliminated all but one plane of oscillation. (all in more detail than I've put here)

Any suggestions as to what I can talk about would be much appreciated. Even if it's not fully related to Malus' Law or Brewsters Law, it would be great to have extra content in my write-up.

Wrichik Basu

Gold Member
2022 Award
Which component/vector of an EM wave (Electric or magnetic) does a polarizing filter eliminate
A filter cannot eliminate both the fields together. In that case, the wave would not be an EM wave.

Consider E-field only. In unpolarised light, the E-field vectors are aligned randomly in all possible directions. When this light is passed through a filter, the vibrations only in a certain plane pass through, and all other E-field vectors are removed.

The B-field vector will vibrate perpendicular to the E-field vector, and will be in a certain plane, rather than in all random directions.

When you read Maxwell's equations, you will find that the E-field and the B-field kind of sustain each other as they pass through vacuum or any media. If one is lost, then it's not an EM wave any more.
Why is reflected light plane-polarized?
A very deep question. You are basically asking for the physics behind what happens at the media boundary so that the reflected light gets plane-polarised, i.e. what interactions occur between light photons and the medium molecules. I don't know the answer, so I'll wait for someone else to answer. In fact, I tried to find this several years ago on the net, but there isn't any good answer. Hope that somebody here gives a satisfactory one.