1.44. Human Vision http://www.ck12.org
FIGURE 1.82
All eyes are on the ball in this basketball
game. Think about how we use the sense
of sight in other games.Seeing in Three Dimensions
Did you ever use 3-D glasses to watch a movie, like the boy pictured below (Figure1.83)? If you did, then you
know that the glasses make people and objects in the movie appear to jump out of the screen. They make images on
the flat movie screen seem more realistic because they give them depth. That’s the difference between seeing things
in two dimensions and three dimensions.
We are able to see in three dimensions because we have two eyes facing the same direction but a few inches apart.
As a result, we see objects and people with both eyes at the same time but from slightly different angles. Hold up a
finger a few inches away from your face, and look at it, first with one eye and then with the other. You’ll notice that
your finger appears to move.
Now hold up your finger at arm’s length, and look at it with one eye and then the other. Your finger seems to move
less than it did when it was closer. Although you aren’t aware of it, your brain constantly uses such differences to
determine the distance of objects.