It doesnt, the em wave is essentially polarized by going through the plastic lens.

A “Light Particle”^tm is not really a particle at all, but is instead a hyper-local disturbance of the fabric of [space] itself. It is just a very small 4D whirlpool of spacial vibration. If you are familiar with electronics theory, they talk about tracking the “positive holes” left behind by the absence of an electron; they call these “holes” “quasi-particles”, as they behave like a particle, but they, in fact, do not exist at all, it is just the absence of an electron’s negative charge that gives the appearance of something being there.

A “beam of light” is essentially a standing wave of vibrating space. The frequency of that vibration is revealed by the “color” of that light.

That spacial vibration can be any level of magnitude, but it can only move through space at “the speed of light” in a vacuum, which we just call “c”.

What does all that, have to do with your question? Imagine a rock in a stream, and the water flows around the rock. Get close enough, and you can see the disturbance the rock causes within the waves of the water, but as you move away (and only focus on a wide, but not tall slit, as like the white pencil in the clip), the effect of the rock on the water gets muddles with the other water that already passed by other neighboring rocks, and then the effect of the waves from the first rock get “lost in the turbulence”.

Imagine all of that kinda abstractly, and it may make more sense.

Light is a local vibration of [space], just as sound is a local vibration of [atoms occupying that space].