How Do We See? Seeing involves more than opening our eyes. Through simple and fun experimentation the class will learn how the interaction of light, the eyes and the brain create the world we see. How Do We See? Our eyes are constantly feeding information to us. When we are born our eyes need time to get used to seeing and understanding what exactly it is that you are seeing. Given time and experience the eyes learn to take in light, focus it and send information to our brain. All that you have experienced to this point has involved seeing and gaining an understanding of all that goes on around you.

Most of what you see involves a knowing of it from previous experiences. We perceive things. We build perception. Perception is not determined simply by looking at something but by our brain searching for the best conclusion of all the available information.

When perception is wrong we are confused. Sometimes the eyes and brain come to the wrong conclusion and we get an illusion or hallucinate. When you look at something your eyes are sending information about color, shape, movement, depth and distance to your brain. Then the brain puts it all together so that you can identify the whole object.

Seeing The first thing one need understand about seeing is that if there is no light one cannot see. We are all able to see because light is bouncing off just about everything. There is more to seeing than meets the eye. When you look at an object you are seeing light that is bouncing or reflecting off of that object. Our eyes can take in light directly from a source, like looking at a light bulb, or indirectly after light bounces off of things like the moon. When light bounces off of the surface of an object some light is absorbed and some light is reflected.

We see only the light that is reflected or bounces off the object, so if you look at something that is blue that something you are looking at is absorbing all of the other colors and bouncing the color blue back at you. The second thing to understand about seeing is the eye and brain connection. The eyes are one of the most important tools we have to gather information for our brain. The Eyes Light passes through a transparent part of the eye called the cornea. The cornea is a lens which bends light inward.

It also slows down the speed of light and provides an adjustable focus. Light is bent further as it passes through a liquid behind the cornea. Next, light passes through the black opening in the middle of the eye. This opening is called the pupil. The Iris is the colorful part of the eye. It is also a muscle that makes the pupil change size depending on the amount of light coming into the eye.

When there is too much light the Iris closes the pupil. Low light or night time, the pupil will expand to allow as much light in as possible. Next, Light travels through a jello-like substance filling the eye called, Vitreous Humor. This clear gel provides a constant pressure to maintain the shape of the eye.

Finally, the light forms an upside-down picture on the back part of the inside wall. This wall is called the retina. The retina is made up of millions of tiny cones and rods called photoreceptors. Rods allow us to see in black and white like animals do. Rods also help us to see where there is little light like night time. Cones come in three different sizes.

(S) Short blue, (M) medium green, and (L) long red. These cones allow us to see in color. Cones and rods encode everything we see and translate the image into a chemical electric message. The message travels along the optic nerve through the thalamus to the back of the brain to the visual cortex. From the visual cortex impulses reach out to other parts of the brain and you and I benefit from an instantaneous mental image of a colorful three dimensional world that we see.