Sugar is something that sweetens food and exfoliates skin, but sugar can be used to do something much more surprising - something that exhibits some really cool physics, chemistry, and math principles. Moreover, it's beautiful and the concepts involved are useful in many areas of science and engineering. Sugar is a chiral molecule and in simple terms, that means that it rotates plane propagating light waves. If you don't understand what that means, you will after my video.
Although I've seen something similar to this done in a lab with much more sophisticated equipment, I haven't seen something like this done with household items, so I was excited to figure out how to do it with common items and share it with you all.
I will explain some of the science at the end of the Instructable.
Step 1: Assemble Items
Some shallow glass dishes
A light source
2 polarizers (2 polarized sunglasses work fine)
Some transparent material (glass, plastic, other substances dissolved in water)
Step 2: Test the Polarizers
Step 3: Find Good Lighting Conditions
You want to minimize light interference, so do this in a dark room or carry out the experiment in a box. The hardest part of doing this Instructable was finding good light conditions.
Step 4: Set Up Light Source and Then Follow Video
Since you will be putting light through a liquid, it's best to shine light from below. You can put the sugar solution and other liquids in glass jars and shine light horizontally (I initially tried this) but there will be more unwanted refraction and reflection since light will be going through at least 2 curved pieces of glass, as opposed to one planar piece of glass.
Step 5: Understand What's Going On
Polarized light is light that propagates in only one plane. In the video, the lower polarizer only lets light oriented vertically through it. Thus, light can't pass through the second, horizontally-oriented polarizer. However, if the light could be rotated before it hits the second polarizer, then the component of that diagonal light that is horizontal will pass through.
Sugar happens to be a substance that can rotate plane polarized light. Sugar is a chiral molecule, which means that it cannot be superimposed on its mirror image (like your hands). When a beam of plane polarized light hits any molecule, its plane of polarization may change. For achiral molecules, these changes cancel out in the aggregate because the mirror image molecule will also be present. This explains why the other substances I put between the polarizers (water, glass, plastic), did not give a net change in the plane of polarization. However, for chiral molecules like sugar, there is no mirror image molecule to cancel out the rotation and so there was a net change in the orientation of light.
I know that this was a bit of a technical discussion, and it's actually even more technical than I have described, but I hope you get a sense of what's going on and that you appreciate sugar just a bit more now.
If you'd like to see more cool, accessible science, please vote for this Instructable. Cheers!