optical illusions

Showing 25 posts tagged optical illusions

We just tried this super easy Reversing Arrow Illusion, and it is, in fact, super easy. Draw two left-pointing arrows on a piece of paper and then put a clear, empty glass between you and those arrows. When you pour water into the glass, you’ll see something that you might not expect. How exactly did that happen? From Physics Central

No, you aren’t going crazy and you haven’t found yourself with Alice in Wonderland staring at arrows pointing in opposite directions.  In fact, you have just demonstrated a physics concept called refraction, the bending of light.

When the arrow is moved to a particular distance behind the glass, it looks like it reversed itself. When light passes from one material to another, it can bend or refract. In the experiment that you just completed, light traveled from the air, through the glass, through the water, through the back of the glass, and then back through the air, before hitting the arrow. Anytime that light passes from one medium, or material, into another, it refracts.

Just because light bends when it travels through different materials, doesn’t explain why the arrow reverses itself.  To explain this, you must think about the glass of water as if it is a magnifying glass. When light goes through a magnifying glass the light bends toward the center. Where the light all comes together is called the focal point, but beyond the focal point the image appears to reverse because the light rays that were bent pass each other and the light that was on the right side is now on the left and the left on the right, which makes the arrow appear to be reversed.

Related mind-benders: the amazing T-Rex illusiona basic demonstration of optical cloaking, and from ASAPscience, Can you trust your eyes?

via The Awesomer.

Gravitational acceleration + optical illusions + how to! In this Get Set… Demonstrate, science teacher Alom Shaha shows step by step how to create Pearls of Water, a physics-defying demonstration that must look even more unbelievable in person than it does on video.

And if you want to see this in person, the instructions, equipment list, and safety notes for setting it up are here (pdf).

Want to see similar versions of this illusion? Check out artist Matt Kenyon’s Supermajor and Brusspup’s Amazing Water and Sound Experiment.

via Science Demo.

Swiss painter, sculptor, and photographer Markus Raetz creates lyrical art that explores illusion and perception. In the piece above, rotating leaves of cut metal reveal a “turning” head in the illuminated space between them. In Yes/No, below, your point of view changes the response given:

You can see more videos of Raetz’s work, including a 10m documentary, at Visual News.

In the archives: optical illusionskinetic sculptures, and perception.

via Sploid.