Sugar lamp

The lamp itself is really simple, the explanation of the science behind it is *significantly* more complicated. So buckle up for a science lesson or scroll down to learn more about the project.

First off, everyone has seen a rainbow from white light shown through a prism. Light waves propagate at different speeds — red being the fastest [having a longer period], violet traveling the slowest [having the shortest period – oscillating more than red]. Notice in the plot below, how in the amount of time it takes the red line to complete one full cycle, the violet line completes about one and a half cycles. When traveling through a medium, such as glass or water, the material affects the speed at which the light moves, slowing it down an redirecting it. This is called refraction.

Another quick concept we have to cover is polarization. These waves that we perceive as white light oscillate in any and every direction all at once. Its honestly sort of a mess trying to depict it. A polarizer is a type of filter that can act as a gate for these waves, only allowing some to propagate when they are oriented in the correct direction.

The image below shows a jumble of waves to the righthand side prior to the polarizing element in the system. Then to the left notice how the only waves that pass through are those oscillating in a single plane.

Then we add in the whole twisting action! This comes from the sugar molecule’s lack of mirror symmetry (called chirality). This means that in any orientation of the sugar molecule, there will never be a non-superimposable reflection to cancel it out.

Circling back really quick to the polarized light, though all the wavelength are traveling in the same plane there are still two possible options as to how it’s traveling — like 0 is to 180, clockwise is to counterclockwise. The plot below shows two sine waves, both waves could pass through the same polarizing filter.

Though, of these two wave, one will have a harder time interacting with the chiral molecule. It could get redirected or bounced around more just based off of which orientation of the molecules it encounters. That will essentially slow the phase of that wave as it travels. The polarized light is the sum of these two parts, and as one slowly beings to oscillate out of phase the path will begin to twist.

This phenomenon called optical rotation, and it has various applications in a wide range of fields including chemistry, pharmaceuticals, and food/beverage industries (think wine — where the purity, concentration and identity of a substances can be determined based on examining the rotation of polarized light).

Combining all these concepts we just explored (color frequencies, polarization, chirality, and optical rotation) we get this really fucking cool twisting rainbow effect just by shining some light into a tube full of sugar and water.

Dubbed the ‘barber pole’ effect, I was inspired to play with science and make my very own barber pole lamp powered by physics.

For some much better explanations with even more helpful graphics please consider checking out the series of videos on light and sugar water on YouTube by 3Blue1Brown and Steve Mould that inspired this project in the first place.

SCROLL DOWN FOR ALL THE DESIGN FILES AND INSTRUCTIONS TO MAKE YOUR OWN LAMP