An Optical Illusion is when one thing looks like two or more different
things.

"Apparition of Face and Fruit Dish on a Beach"
For
example, in the painting, "Apparition of Face and Fruit Dish on a
Beach", by: Salvador Dali, one part looks like a dog but also looks like a
bridge leading to a road, on a mountain, with a tunnel going through the
mountain. One part is a fruit dish but also looks like a face or a lady sitting.

"Mae West"
"Mae West", by: Salvador Dali, looks like a lady’s face but the
eyes look like two paintings, the nose looks like a table with a diamond on it
and the hair looks like curtains.

"Human Condition"

"Human
Condition", by: Rene Magritte, looks like you are looking in the window but
half of it is a painting of the outside. But the painting is on an easel and you
can hardly see it. It just looks like you are looking at a window.

"Les Trois Sphinx De Bikini"

In
"Les Trois Sphinx De Bikini", by: Salvador Dali, there is a tree with
white leaves on it but it also looks like the back of someone’s head with
shampoo on it.

From reading this section you now know many interesting facts about Optical
Illusion. You also know how artists seemed to change a picture by adding things
that makes it an Optical Illusion.