A Candle in the Dark

A look on science, politics, religion and events

Optical Illusions

with 6 comments

These are some really neat optical illusions. Many optical illusions are beautiful, astonishing and powerful. I think they show how easy it is to fool the visual system and the brain.

Same color illusion

In the above image, look carefully at the squares marked as A and B. One appears white and the other appears black, right?

Amazingly, both the squares have the same color! Don’t believe it?

To verify that the color’s are the same, try cutting the two squares and place them side by side in paint or photoshop. Or, you could use the colorpicker tool to check that the colors are the same.

There’s an explanation of why this illusion works at the MIT site.

Scintillating Grid Illusion

This is a famous one. You’ll see the sudden appearance of black dots at the crossings. Also, if you keep your eye fixed on a particular intersection, no dots appear there.

I wasn’t able to find any explanation on how this illusion actually works.

Peripheral drift illusion

Click on the image to get a larger version

The ‘rotating snake’ illusion is one of my favorites. The ‘rotation’ of the wheels occurs relative to your eye movements. It’s thought that asymmetric luminance at the periphery of the vision causes this illusion.

Click on the image to get a larger version of the illusion.

Afterimage illusion

Keep concentrating on the sign at the center of the circle.

Do you see the rotating green spot?

Fraser’s Spiral

Actually, there are no spirals!
The intersecting black arcs appear to form a spiral, but they are in fact concentric circles.


Parallel or not?

External Resources

70 Optical Illusions & Visual Phenomena by Michael Bach
Optical Illusions, Wikipedia


Written by parseval

March 8, 2007 at 8:00 pm

Posted in fun, physics

6 Responses

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  1. Thank you for the comment, good sir! I’m glad you liked it 🙂

    Mohan K.V

    March 9, 2007 at 11:46 pm

  2. Nice set of illusions. 🙂


    March 18, 2007 at 7:41 pm

  3. I was searching the internet for an answer to this. Have you ever noticed the optical illusion with flickering candles? If you are sitting in the dark and there are flickering candles, if you stare at the candle and ‘concentrate’ you can make the candle stop flickering. Unfocus your eyes, look away, and it starts flickering again.

    Do you have a reference for how this illusion works?



    John W. Ratcliff

    January 13, 2008 at 8:07 am

  4. Wow what a collection wow i liked most the one with the drift ilusion because if i focus on one circle the others are like burning or melting something
    And sorry for my bad english im from greece 🙂


    August 24, 2008 at 1:04 am

  5. I was just searching for a Illusions,
    and I was working about a Illusions in Kardinia
    (I’m from Korea, not the North Korea, South Korea..^^)=))


    March 9, 2009 at 10:22 pm

  6. Flipped my lid sir. Flipped. Lid.


    September 10, 2009 at 2:48 pm

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