Why is it that clear plastic sheets begin to display a colour if you fold them onto themselves enough times?

849 views

Flaired as physics because I assume it has something to do with photons and diffraction.

I was folding up my plastic table sheet and noticed this, that the originally clear sheet was now an off yellow. Sometimes some plastics appear distinctly blue, but never clear, as it would be when you are looking through just one layer of the plastic sheet. Folding it so you’re looking through two, then four, then eight layers, etc, changes the colour and makes it more distinct. Why is this? Are the sheets actually not clear and have a small hue to them? Thank you!

In: Physics

Anonymous 0 Comments

So you know how color can be made up of different primary colors combined together?

Red green and blue for color of light.

With an even amount of red, green and blue light, you get white light.

Say you have a thick enough blue plastic that blocks 100% of red and green while letting blue light through.

You will perceive this plastic as blue, true blue.

Cut this plastic in half. Now it can only block 50% of red and green, but still can allow 100% of blue light through.

With the addition of red and green, the blue color looks washed out and more faint.

Cut it in half again, 75% of red and green light gets through. As you can see, with this much thinner plastic, you are approaching having all 3 primary colors be the same intensity. 75% is very close to 100%.

As you thin out the plastic more and more and more, the intensity of red and green light is let through more and more.

With something like plastic wrap, it is so thin that the original color is completely unnoticeable because it is unable to block most of the light it should.

If you fold the plastic wrap, you are increasing the amount of light it can block by doing the opposite of what is described above.