Playing with Optics

By Shah Kasmuri, Science Educator @ The Tinkering Studio, Science Centre Singapore.

They say seeing is believing. But can we really trust what we see?

Long before scientists were studying the properties of neutrons, artists had devised a series of techniques to deceive the brain into thinking that a person can be sawed in half, survived, and then joined together again.

Illusionists are entertainers and they entertained us in a very specific way. They often leave us puzzled and curious by their illusions, which intrigues us to understand how those deceptions work.

What is an optical illusion

An optical illusion is something that plays tricks on our vision. Optical illusions teach us how our eyes and brain work together to see. We live in a three-dimensional world, so our brain gets clues about depth, shading, lighting, and position to help us interpret what we see.

When we look at a two-dimensional image, our brain can be fooled because it does not get the same clues. Take a look at the optical illusion below. Can you figure them out?


Which mouth is longer? Make a guess and measure them to find out


Safety Pin trick


toothpicks-69150.jpgLet’s do it!

I am no illusionist, but I am taking this opportunity to share a magic trick I often used to break the ice while waiting for dinner to be served.


  1. Take a safety pin and push a piece of toothpick thru the middle of it. Ensure that the toothpick and rotate or revolve on the pin.
  2. Close the safety pin and turn the position shown in Diagram 1.1.
    Press its lower end and try not to break the stick.
  3. Release the toothpick with a snap and it will apparently pass through the safety pin like magic.

Click here to see the video!

The Science behind it!

The toothpick went through the pin! Of course, it did not.

Information gathered by the eyes are processed by the brain, creating a perception.

The toothpick revolves back when snapped. The action was so fast that it creates a disconnection between perception and reality. This is what we call “Visual Illusion”. It demonstrates the way in which the brain fails to re-create the physical world.

The Evidence

Colour one end side of the toothpick and snap it again. Now, take note of the coloured positioning. You will notice that it had flipped over to the other side of the pin.
Congratulation! You have just debunked this trick.

Investigate more illusion versus reality by visiting The Mind’s Eye exhibition, at Science Centre Singapore.

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