Lines

Perspective can cause you to see lines differently depending on how they are presented. If you drew three equal lines, but drew slanting lines on the end of each as in the figure below, the added lines would change the way you see them. The top line looks bigger and the bottom line looks the smallest.

But this illusion can be destroyed if you change the order of the lines. Below the lines now appear to be the same length.

Sometimes we see things differently because of what its surroundings. If you look at the figures below, one of the circles looks bigger in each figure, but they are really the same size. Can you figure out why?

You can also use straight lines to make a circle appear top bend, and circle to make straight lines appear to bend. If you put a circle around a square, the circle appears to pinch in at the point where it touches the square.

If you put a series of circles inside that same circle, the lines of the square appear to bend. Even the direction you look at something may make something look different to you. The two squares below are the same size, but the one on the left looks bigger because it is turned to be a diamond. So how you look at something and what surrounds it adds up to the perspective and that adds up to optical illusions.