Optical IllusionsWERC

Visual Acuity

Part 1

Visual Acuity• Definition: sharpness of vision, measured by the

ability to discern letters or numbers at a given distance according to a fixed standard.

• If you have glasses, you don’t have good visual acuity. If you have 20/20 vision, however, you have good visual acuity.

• The visual acuity test is more commonly recognized as the Snellen Chart. It is used to test eyesight to see if patients need glasses.

What does visual acuity show about a person?• Visual acuity shows that a person pays large

attention to detail. They also think outside the box when it comes to simple things.

• The Snellen Test shows how well or how poorly a person can see.

How is visual acuity used in real life?• It is often used to test eyesight.• Fun Fact: Astronauts have to get their eyes tested

so that they can be positive of what they’re seeing in space.

Eyesight Tests

Part 2

Lines Upon Lines upon Lines

Test #1

Which of the yellow lines is bent?Neither. The yellow lines just appear to be bent because of the black lines “push them out.”

The Saxophone

Test #2

Look at the picture to the right.What did you see first?

Some people see a man playing a saxophone, but those with better eyesight see a woman.

Man With Saxophone Woman

Lines of Illusion

Test #3

Which side of blue seems brighter, left or right?The right side seems to have a brighter shade of blue, but both sides have the same shade. Since red is the opposite color of blue, it makes the blue pop out more.

Makes Your Head Spin

Test #4

Which circle is bigger?Both circles are the same size. The purple/red circles surrounding them make them seem bigger/smaller than they actually are.

Road to Illusions

Test #5

Which of the purple lines is longer?Hint: Don’t pay attention to the width of the line, just the length.

A Helping Hand

Test #6

Does the drawing of the hand look 3D?

Does the drawing of the hand look 3D? What if it’s turned like this?

Depending on your point of view, the hand looks like it either pops out at you are divots because of the curved lines.

3D Divot