Some optical illusions occur naturally. They are all around us. Strange illusions appear in the sky, certain animals can blend into their surroundings, or look like something completely different. On some clear days at sunset, the upper rim of the sun appears for a few seconds. This is called the green flash.
A rainbow is a natural optical illusion that can appear when sunlight reflects off raindrops. The light from the Sun is bent as it travels through the drops. The different colors that make up white light do not bend at the same angle, so they split into the seven colors of the spectrum.
On sunny days, pools of water seem to appear on the road. This is known as a mirage. The light has got curled by the rising hot air close to the ground. The expanding hot air also makes the light shimmer, giving an overall effect of rippling water.
Some animals have evolved ways of hiding themselves from other creatures. They use camouflage. A lion has sandy-colored fur to make it hard to see in the long dry grass.
The stick insect, as its name suggests, has evolved to look like a small twig. Peacock and butterflies scare off predators with the vividly colored circles on each wing. These look like a pair of ferocious eyes.
A Zebra, which might be a lion’s prey, are marked with irregular black and white stripes. The stripes make it hard for the lions to tell one zebra from another in a large herd.
