Optical illusions vary from complex to simple. Many of the more-complex optical illusions are hard to replicate and may not be doable at home. But there are simpler illusions that are easier to replicate and may even be basic enough for children to do. These easy optical illusions are fun for kids and can be educational as well as part of lessons about vision.
Cut out a shamrock from red paper, making it about 5 inches tall. Paste the shamrock on a plain white piece of paper. Hold the paper with the shamrock up, with another plain piece of white paper right next to it. It should be about eye level for the child or children. Ask them to stare for 30 seconds at the red shamrock. Then, have them stare at the plain white paper. The child should now see a green shamrock on the white paper, even though no green shamrock exists. Staring at red for so long causes the eye to next see green, even if it may not exist.
A few supplies are needed for this project including a compass, protractor, plain white paper, pencil, coloured markers and a pen. Place the point of the compass in the middle of the page and swing it around to make as large a circle as you can without straying off the page. Draw several smaller circles inside the large circle, being careful to create at least three distortions. Distortions occur when three or more circles are drawn extremely close together. Place the protractor inside the largest circle and mark off each half and full degree. Turn it upside down and mark the other half of the circle in the same way. Use a ruler to mark lines out from centre of the large circle to the end of the page. This should create blocks all over the page. Now use the coloured pencils to colour in the checkered spaces in various colours. Once coloured in, the page should look like it's moving.
Neon Mini Sign
Take a file folder or other thick paper and cut out a rectangle twice as large as you would like your sign to be. Fold it in half to make a crease, then unfold it. Draw a picture and write some text in each square, whatever you want your sign to say. Turn the card back over to the undecorated side and spread the edges with glue. Fold the card on the crease again, making sure to stick a straw between the backs of each square to form your sign. Allow it to dry, then twirl the straw quickly between clasped hands. The optical illusion should show both sides at once. This is because it is being twirled so fast that the eye hangs on to each side for seconds even after the image is gone.
Cut a circle out of cardboard that is about 1.5 inches in diameter. Use this as a template to cut out two more circles, but on plain paper instead of cardboard. Draw a lightning bolt on one of the paper circles and a cloud on the other. Glue one circle on each side of the cardboard circle. Punch two holes in the newly joined circle, one on top and one on the bottom. Push string through each hole and secure it with a knot to form a loop. Twirl each loop of string until the circle in the middle begins to twist. The twirling will happen so fast that it will look like the lightning bolt is coming out of the cloud, even though they are on opposite sides of the circle.