The Trickery and Deceptions of Light Part 1

Awkward Aquarium Moments:

Recently, my wife and I visited a local aquarium with a couple of friends of ours. This particular aquarium is one of my favorites because it caters to the inner child in me. At this aquarium they have a large number of interactive exhibits where you can touch, feed, and even hold the animals. We were nearing the end of the aquarium loop when we had finally reached one of my favorite exhibits: the stingrays. There, we get to feed shrimp to the stingrays and even reach into the tank to pet them as they pass by. Eager to impress my friends, I quickly jumped up to the edge of the tank preparing to pet the first stingray that passed me. The scene was reminiscent of a kid running to the curb as the ice cream man slowly pulled up to the side of the road. But unlike the ice cream man scenario, there was more than just air between me and the stingrays. There was air, then water. Doesn’t seem stressful now, but just you wait! As I reached into the tank to pet the first passing stingray, he appeared much closer than he actually was and so I nearly toppled into the aquarium reaching down to pet the stingray… Whatever machismo I thought I had practically fell into the tank with me.

So what happened here? Did I run to get my eyes checked after this embarrassing incident? Nope, I was simply fooled by the master trickster known as “light.” As light passes through one substance (like air) and into another (like water) sometimes the light will bend. We call this phenomena “refraction.” As light travels into a new substance and bends, the light may also travel faster or slower than normal. These characteristics of light causes the image we see to be slightly out of the ordinary. In my case, the image of the stingray I was seeing became slightly enlarged and at a surprising depth.

 

Examples of Refraction Illusions

Somewhere Over the Rainbow: While we are on the subject of going to an aquarium and unleashing your inner child, how about chasing after a rainbow and finding that ever illusive pot of gold you heard about as a kid? Well you can cross that off your bucket list because you will never find that pot of gold and the rainbow itself is an illusion! Who’s the culprit of this illusion?! You guessed it, the ever devious visible light. But visible light has an accomplice in this trick: the sun. The sun gives off white light. White light is a combination of all colors within the spectrum of visible light. On a rainy day, tiny drops of water accumulate in the air. As white light passes through these tiny drops of water in the air, the light bends at a 42 degree angle. As the white light bends (or refracts) it breaks apart into the various colors that make up a classic rainbow. The raindrops can produce all colors of visible light thanks to refraction, but we only see each droplet expressing one color of light at a time because of the angle the light hits our eyes. The closer or farther you get, the rainbow may remain visible or disappear depending on the angle of the refracted light. If the moisture in the air vanishes, so too does the rainbow since there is no water droplets for the light to pass through.

So let’s review all the key steps to this magic trick: Visible light from the sun travels through air and then refracts as it passes through tiny rain drops. The refracted light bends at a 42 degree angle and produces the beautiful colors of the rainbow. The refracted light travels to our eyes at distinct angles and thus we see a rainbow.

So you can never actually arrive at a rainbow and climb on it to reach the road to the Greek Gods and if you encounter a leprechaun trying to give you directions to the pot of gold at the end of the rainbow, it’s a lie! However, your childhood adventures searching for the pot of gold were not completely fruitless, at least you have epic memories of your adventures to cherish.

Check out this awesome video by “It’s okay to be smart.” They teach you the truth about rainbows better than I can: https://www.youtube.com/watch?v=5pYnC-ONdXQ&t=197s

Did you know?! Visible light lies in between Ultraviolet light and Infrared light on the electromagnetic spectrum. We can only see the “visible light” portion of this spectrum. But certain animals can see other portions of the spectrum as well. Honey bees and birds can see in Ultraviolet light. Bees use UV light to help guide them to flowers. Infrared radiation is commonly used to detect heat. Snakes have evolved the capability of seeing in Infrared to help them detect their next meal.

The Broken Pencil: This example is the same concept as my awkward moment at the aquarium with the stingrays. Try placing a pencil in a glass of water. What do you see? A split pencil? An enlarged pencil? As light travels through the air, it travels in a straight line. But once the light passes into a new medium (“medium” is another word for substance, for example water or glass) it bends. Once the light bends, it distorts the image we see. Depending on the angle we are looking at the pencil and where in the glass of water the pencil is, it may look enlarged and broken. That is because light deceives our brains once more. As the refracted light travels back to our eyes, our brain tries to make sense of the information from the light. Our brain assumes that light travels in a straight line and has a difficult time accounting for the effects of refracted light. Thus our brain interprets the new image of the pencil to be enlarged, or split. Of course, if you jump into the water with the pencil, it would look like a normal pencil because now light is only passing through one type of medium (water) to get to your eyes. Light is the ultimate magician!

Why do stars twinkle: Ever since I heard that classic children’s song, I have always looked into the night sky for the twinkling stars and sometimes I see them. But are the distant stars themselves “twinkling?” The short answer to this is no. The light from stars don’t just fade in and out like a loosely connected light bulb. So how is light messing with our brains this time? This time, particles in the atmosphere team up with visible light to trick our eyes. Our atmosphere is made up of a wide variety of gaseous elements and compounds. As light passes through these various particles on its way to meet our eyeballs, it bends and shifts ever so slightly (refraction again appears to be the culprit). Thus the star itself isn’t twinkling, but the light from that star shimmies ever so slightly on its course to our eyes because of the gas particles in our atmosphere.

Word of the Week: “Refraction:” The phenomenon of light bending as it passes from one type of medium into another. The angle at which the light bends can vary. The value of the angle of refraction is known as the “index of refraction.”

If you read this whole blog post, you are my hero! Thanks for reading. Please feel free to leave me a comment and feedback below. Also, let me know if there is any particular science topic you would like me to look at “through green tinted glasses” and I will write about it.