Optical Illusions

By Zach

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Trick or treat? Either way you’ll get an optical illusion. Why trick? An illusion is a trick on your mind. On a hot day have you ever seen what looked like a puddle on the road, but when you get closer there’s nothing there. Well that’s called a mirage. A mirage is an illusion. Why a treat? Easy, illusions are fun stuff. People have always loved illusions but they’ve never paid much attention to why they’re so much fun. Lucky you, you’ll get to learn all about that. Plus, I might have a trick or two up my sleeve. Welcome to optical illusions.

  Vision may seem easy. For example you will see a blue sky and say “OH! How beautiful!” instead of saying, “OH! How do I see that?” Only in the last century and especially in the last twenty years have scientist been able to make a little sense of what happens in your eyes. Take some time to look around; when you tilt your head the world doesn’t tilt. When you shut one eye you don’t lose depth perception. Look at what happens to different colors under different light, white light, and no light and colored light. Move around an object the shape you see changes, yet it stays constant in your perception.   Your brain sorts the images not your eye.  An illusion works because your brain encounters something unusual but tries to interpret it in the set of rules it knows.

Color Illusions

Color illusions are illusions that use color to trick you. An example of a color illusion is when you stare at a light or the sun and then you look away you see an after image of the light. If you look at a shaped light (a light that you might see at a restraunt such as a neon open sign) you will see a fuzzy enlarged version of the light. If the light is colored you will see the opposite color when you look away. For example if the light is green, the color when you look away will be red. Opposite colors are called complementary colors. Other complementary colors are blue and orange and yellow and purple. Look at the color wheel for a visual example. The colors of a rainbow are called a spectrum. 

Rods, Cones and Wavelengths

Rods, cones and wavelengths. Rods and cones, you’ve probably heard these words before but not in the definition that I’m about to give you. And wavelengths, what the heck are those? Well I’ll tell you. Rods and cones are nerves cells in your eye. Cones let us see color, while rods let us see shades of light. For example, you cones see blue your rods make your eye see if it’s light blue or dark blue. At night your eye lacks most of the cones that there are during the day. Why because at night the two main colors are black (dark) and white (light). However they are not completely gone, at night if you look at something with color then you will see a very, very dark version of that colored object, but it will still be colored. There are more rods than cones at night but there aren’t very many rods in the center of the pupil so if you stare straight at a star after a while it will dim almost out of sight. That is because of the absence of light sensitive rods in the center of the pupil. However if you glance away then the star will suddenly brighten. That is because the stars image is falling on the rods around the edge of the retina. In day, however there is much more cones that is why you see the red stop sign and the brown bird and the blue sky. Speaking of colored objects where do they get their color? Wavelengths are how they get their color.

A wavelength is white light in different lengths. Certain lengths reflect certain colors and the reflected color is the one you see so the sky absorbs every wavelength except blue, it reflects blue that is why on a sunny day you see a blue sky. Another example is the title, it absorbs all the wavelengths except red, and it reflects red that is why you see, well, red. Wavelengths come from white light because white light is all the primary colors mixed together. If you took all the crayons in the world and melted them together you would probably get some weird throw up color. If you could melt the colors of a rainbow together they would turn virtually invisible.  If you’ve heard of a prism, which you might not have which is fine I’ll tell you what it is, it is an object that splits white light into the colors of a rainbow. With a prism you can split the colors but you can also put them back together with a prism. Try this at home. If you have any prisms at your house take two and then turn out the lights and make the room dark. Turn on a flash light and use a magnifying glass to focus the light and shine it on a prism a rainbow appears then use another magnifying glass to focus the rainbow on another prism out comes white light! You might need help from a parent or friend.

Geometric Illusions

  Geometric illusions, ah, my favorite. This is where you get all the impossible stuff and the things where you think one thing is longer but it is not. Well here’s the science behind all that. In geometric illusions your brain is influenced by other parts of the picture. When you are influenced by the other parts it is impossible to see what you really need to see. Some illusions work when you don’t know everything for example you don’t know how long an object is or that they’re the same size because the picture won’t tell you that. But your brain thinks that one is longer because another line influences your brain. Look at the lines on the left for a visual example.  Which one of the lines is longer? The left one is right. Wrong! They are the same, don’t believe me? Measure it. The left one looks longer because the lines at the top and bottom appear to “open out” drawing your eyes with them. In impossible shapes people draw 2.D. shapes so that they look 3.D.

Let’s go over what I said. Color illusions happen when you look at a light and see an afterimage (I wouldn’t look at the sun for an afterimage). Rods and cones are nerve cells in your eye wavelengths are lights in different lengths. Geometric illusions are illusions that don’t give you full information. Well that’s all the tricks and treats of optical illusions I have for you. to go back to the museum ex out of this article.


Kettelkamp, Larry. Tricks of Eye and Mind. New York: William Morrow, 1974.

Simon, Seymoure. The Optical Illusions Book. New York: Four Winds Press, 1976.

Patrick Green and Ian Howarth. Unlock the Secrets of Your Mind. New York:
Tangerine Press, 2000. Print.

Seckel, Al. The Art of Optical Illusions. Dubai:Carlton Books, 2000.

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