Optical Illusions and Brain Teasers

Hi! Sorry I haven't posted since the 5th....
Today, I'm gonna be posting some brain teasers and visual illusions from

There are three switches downstairs. Each corresponds to one of the three light bulbs in the attic. You can turn the switches on and off and leave them in any position.
How would you identify which switch corresponds to which light bulb, if you are only allowed one trip upstairs?

Keep the first bulb switched on for a few minutes. It gets warm, right? So all you have to do then is ... switch it off, switch another one on, walk into the room with bulbs, touch them and tell which one was switched on as the first one (the warm one) and the others can be easily identified :-)

Your last good ping-pong ball fell down into a narrow metal pipe imbedded in concrete one foot deep.
How can you get it out undamaged, if all the tools you have are your tennis paddle, your shoe-laces, and your plastic water bottle, which does not fit into the pipe?

All the tools are random things that are not going to help you. All you have to do is pour some water into the pipe so that the ball swims up on the surface. And if you say that you don't have any water, then think about what you drank today and if you can use that somehow :-)


This logic puzzle was published in Martin Gardner's column in the Scientific American. You are in a room with no metal objects except for two iron rods. Only one of them is a magnet.
How can you identify which one is a magnet?

You can hang the iron rods on a string and watch which one turns to the north (or hang just one rod).
Gardner gives one more solution: take one rod and touch with its end the middle of the second rod. If they get closer, then you have a magnet in your hand.
The real magnet will have a magnetic field at its poles, but not at its center. So as previously mentioned, if you take the iron bar and touch its tip to the magnet's center, the iron bar will not be attracted. This is assuming that the magnet's poles are at its ends. If the poles run through the length of the magnet, then it would be much harder to use this method.
In that case, rotate one rod around its axis while holding an end of the other to its middle. If the rotating rod is the magnet, the force will fluctuate as the rod rotates. If the rotating rod is not magnetic, the force is constant (provided you can keep their positions steady).


A Petri dish hosts a healthy colony of bacteria. Once a minute every bacterium divides into two. The colony was founded by a single cell at noon. At exactly 12:43 (43 minutes later) the Petri dish was half full.
At what time will the dish be full?

The dish will be full at 12:44.


An Arab sheikh tells his two sons to race their camels to a distant city to see who will inherit his fortune. The one whose camel is slower wins. After wandering aimlessly for days, the brothers ask a wise man for guidance. Upon receiving the advice, they jump on the camels and race to the city as fast as they can.
What did the wise man say to them?

The wise man told them to switch camels.


I hope you enjoyed these brain teasers!! Now time for some optical illusions!

Profile of Salvador Dali and a strange woman.
Dali Illusion

Can you find both? Rabbit is looking to the right and duck to the left 
Rabbit and Duck 2

This is a bistable illusion where you can see movement both clockwise and counterclockwise. It is NOT a test to determine which hemisphere is dominant
Spinning Silhouette Dancer

Fantastic static image
Crawling Snakes

Stare at the red dot on the girl's nose for 30 seconds. Then look at the ceiling (or any white surface) and blink really quickly a few times. You will be amazed to see a colorful girl.
Girl Afterimage

Surface color of both A and B parts is identical. Just use a finger to cover the place where both parts meet and you'll see.
Identical Colors

Both green lines have the same length. This Ponzo illusion uses the fact that human brain interpretes the image with perspective, however, it's just a simple 2D image.
Ponzo Illusion

The Terrace (by David akeMacDonald)
The Terrace

That's all for now!! I hoped you enjoyed!! ~Cupcake :D


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