Have you ever witnessed an illusion that left you awe-struck? Whether it would be from birthday party magicians to those weird recommended videos on YouTube (that we ALL have watched at some time), somewhere, at some point your brain has been fooled. Magicians have been able to deceive our perceptions with their mastery of sleight of hand, but what about any illusions that don’t use this technique? Thankfully, we don’t need a magician to know the “secrets” of light interactions, so we can try examining those.

Here’s an example of a pure illusion that you may have seen before and that I had been reintroduced to in my general chemistry course this past week. Take a look at the image of the colored circle. Focus on it by staring at the white dot in the middle for 30 seconds. After 30 seconds, look at the white space on the right and blink rapidly. Can you tell the difference? If you did it correctly (congrats, you’re not color blind!), you would have noticed how the colors in the 3 arcs: blue, red, and green, have changed into different colors: yellow, cyan, and purple-like respectively. How does this trick work though?  

To examine this, we need some background knowledge about light and its interactions with matter. Simply put, light is a form of energy that is dual-behavioral depending on whether the wave-like behavior of electromagnetic waves or the particle-like behavior of photons (quantum of light) is being observed. Let’s first examine light under the scope of wave behavior. 

Waves can be interpreted in many ways through defining characteristics of their oscillations; some of these being the wavelength (peak-to-peak or troph-to-troph distance), frequency (the rate at which waves pass through a single point), speed (a constant “c”= 3 x 108m/s), and amplitude (height/intensity of light). Generally, frequency and wavelength are inverse to one another, since increasing the frequency of a wave means the distance between wavelengths will shorten and vice versa. 

If we were trying to identify the properties of waves, we would do so by examining their wavelengths. The spectrum of electromagnetic waves can represent this visually for us. The range of these wavelengths of electromagnetic radiation varies from microscopic units of angstroms (1 x 10^-10m) which are found in highly energetic gamma rays to kilometers (1 x 10^2m), found in radio frequencies. Visible light represents a narrow region of this spectrum that can be seen by the human eye from 400-750 nm and contains the various wavelengths of this range corresponding to different colors of the rainbow (we’re getting somewhere). 

Since we just analyzed light interactions with wave behavior, it’s only fitting we complement it with the applications of the interaction of light with matter. There are four notable light interactions with matter: emission, absorption, reflection, and radiation. For the sake of relevance, we will only be discussing absorption. Absorption occurs when white light is transmitted through an object, while the wavelengths of its complementary color (as seen on the color wheel), are absorbed by and contribute energy to the solution (this is what’s important). You may be thinking, “Why would the complementary color of a solution be absorbed instead of the color being transmitted through?” To expand on that, that’s just the way it is. Since Isaac Newton discovered white light could be separated into colors, he was able to arrange this relationship into what is now a color wheel, revolutionizing what complementary colors would be. 

How we observe colors is determined by how our eyes process them. Physiologically, the photons in the visible range of electromagnetic waves are detected by the cone and rod cells in the retina and are then processed by the optic nerves in the back of the eye to be interpreted by the brain. 

There is still more to this topic, but the information we have now is sufficient enough to come to a conclusion about the illusion mentioned in the beginning. 

The illusion of the changed colors was able to fool our brains because normally our eyes subconsciously process visual light in absorption for us, presenting the result of the transmission and residue of the complimentary wavelengths through the corresponding color of the object. Once those receptors were overworked (staring for 30 seconds), a temporary image with complementary colors was able to be seen when continuously blinking. The disconnect from the overworked receptors allowed us to get a glimpse of the conversion for ourselves in a simple, but fun little optical illusion. 

______________________________________________________

Attached here is another cool example of this illusion with Ryan Gosling as Ken from the Barbie Movie if you would like to try!