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Optical Illusion Science Projects

Explore optical illusions and trick the eye with these science fair projects, experiments, and STEM activities.

Series of index cards for a flipbook to explore apparent motion, one of highlighted science projects about optical illusions

How Do Optical Illusions Trick the Eye?

Optical illusions (also called visual illusions) can be fun, mind-boggling, mesmerizing, puzzling, and surprising! Our eyes don't always see what they should. An optical or visual illusion occurs when there is a disconnect between our brain and our eyes or when something goes wrong in the visual process. Science related to light, vision, and perception can help explain these tricks of the eye. With the science and engineering projects and experiments highlighted below, students can explore how optical illusions work and even create their own!

Explore the Science of Optical Illusions

Use the resources below to conduct independent science projects related to optical illusions or explore with short STEM activities or classroom lessons.

Optical Illusion Experiments

Optical Illusion Science Projects

Beginner

  1. A Puzzling Parallax: explore how parallax can be used to measure how far away distant stars are. Use hula hoops to investigate how the distance of a nearby object is related to how far it appears to move when you view it from different perspectives.
  2. Apparent Motion & Animation: learn about flip-books, thaumatropes, phenakistiscopes, and zoetropes, four devices that can be used to create animation or apparent motion. Then make simple flip-books from index cards to explore the apparent motion illusion and the persistence of vision phenomenon. These examples of human perception help explain how we perceive movement when watching cartoons or stop-motion animation.

Intermediate to Advanced

  1. Are Your Eyes Playing Tricks on You? Discover the Science Behind Afterimages!: investigate how human cone cells respond to various colors by experimenting with afterimages.
  2. Build a Levitating Water Fountain with the Stroboscopic Effect: create an optical illusion of water falling "up" by combining a DIY fountain with a strobe light. As an extension, make your own strobe light using an LED strip and Arduino.
  3. Design Your Own 3D Printed Optical Illusion: use MATLAB or Python in this math-based project and design (and 3D print) your own "impossible" shape that creates an anomalous mirror symmetry optical illusion. When rotated in front of a mirror, the reflection always points the other way! The project shows an arrow example, but what 3D shape(s) can you create for this illusion?
  4. Explore Optical Illusions: Build an Infinity Mirror: use LEDs and mirrors to design and build an infinity mirror. Look inside, and it looks like you are peering into an endless lit tunnel. This is an engineering design project. No programming is required, but students can add coding and extend the exploration with the Use an Arduino™ to Control a Color-Changing Infinity Mirror project.
  5. Human Perception of the Anomalous Mirror Symmetry Illusion: expand an investigation of shapes like the "impossible arrow" by designing a custom project to explore specific factors that may affect human perception of anomalous mirror symmetry illusions.
  6. Now You See It, Now You Don't: A Chromatic Adaptation Project: experiment to see how quickly your visual system adapts to a constant stimulus by exploring chromatic adaptation. How long does it take for your eyes to adjust?
  7. The Wagon Wheel Effect: explore the relationship between an object's rotational speed, a camera's frame rate, and the resulting apparent motion that can make spinning blades appear to be spinning backwards or not moving at all.
  8. I See a Full Moon Rising...and Shrinking...or Do I?: use afterimages to investigate Emmert's law and "angular size" to explore the full moon illusion. What is the magnitude of the full moon illusion (or how wrong is our perception of the size of the full moon)?

Quick Optical Illusion Science Activities for All Ages

  1. Afterimages: The Colorful Tricks Eyes Play: learn about afterimages, images you see after staring at an object for several seconds and then looking away, and observe an afterimage that helps explain how our eyes see color.
  2. Apparent Motion in Flipbooks: make flip books with index cards and test to see if changing the spacing of the image (or dot) on each card makes a difference in the apparent motion created when flipping the book.
  3. Can you see your Hole hand?: learn how the brain processes information from our two eyes and then see what happens when you try to trick the brain by having your eyes send different information about what you are seeing.
  4. Distorted Images in Curved Mirrors: make your own flexible funhouse mirror and explore the wacky world of curved mirrors while learning about concave and convex mirrors.
  5. Seeing Science: The Size of the Full Moon Rising: learn about Emmert's law and how it helps explain why the full moon appears bigger at the horizon than it does when it is higher in the sky.
  6. Starry Science: Measuring Astronomical Distances using Parallax: experiment to see how parallax helps explain why closer stars appear to move relative to distant stars as the Earth's position changes.
  7. The Ambiguous Cylinder Illusion: 3D print the shape to try this optical illusion. When viewed from one side, it looks square. When viewed from the other side, it looks circular.
  8. The First Cartoon: Make Your Own Thaumatrope!: make a paper version of a classic toy that creates the illusion of a simple animation as it spins.
  9. The Impossible Arrow Illusion: 3D print a readymade file to explore the "impossible arrow" illusion firsthand. No matter how many times you spin the arrow around, it always seems to point in the same direction, but its reflection always points the other way!
  10. The Wagon Wheel Effect Optical Illusion: learn about the wagon wheel effect and see it in action using a fan or a drill.
  11. When a Flashing Light Shows More: use egg beaters to investigate the stroboscopic effect.

Optical Illusion Lesson Plans

  1. Design Your Own 3D Optical Illusions: guide students in designing their own 3D objects that exhibit "anomalous mirror symmetry." When these objects are placed in front of a mirror, their reflections appear flipped left to right. (Working MATLAB and Python code is provided. Your students do not need to write the code from scratch.)
  2. Fool Your Vision to Find Out How It Works: explore how our vision works with two hands-on experiments. At the end of the lesson, students will be able to explain why they saw a hole in their hand (that wasn't really there) and why they saw colors (afterimages) that were never there in the optical illusion activities.
  3. Two Eyes Are Better Than One: investigate vision, seeing with two eyes, and how parallax contributes to depth perception. Students do two short experiments: "There's a hole in my hand!" and "Pencil Parallax."

Optical Illusion Experiments in Action

The following STEM videos demonstrate some of the projects and activities highlighted above:

Vocabulary

The following word bank contains words that may be covered in projects, lessons, and experiments about optical illusions:

  • Additive light mixing
  • Afterimages
  • Animation
  • Angular size
  • Anomalous mirror symmetry illusions
  • Apparent motion
  • Binocular vision
  • Chromatic adaptation
  • Concave
  • Cone cells
  • Convex
  • Depth perception
  • Emmert's law
  • Flicker fusion threshold
  • Full moon illusion
  • Light-sensitive cells
  • Optical illusion
  • Parallax
  • Perception
  • Persistence of vision
  • Sensory receptor fatigue
  • Sensory receptors
  • Stroboscopic
  • Thaumatrope
  • Visual illusion
  • Wagon wheel effect

Owl eye image adapted from "Eye in You" © 2015 Mike Cofrancesco, used with permission in Two Eyes Are Better Than One.



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