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Make an Artificial Eye

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The human eye is a fascinating organ that works much like a camera does.  Here is a way to mimic an eye from ordinary objects so you can see how one works for yourself.

Things You Need

Goldfish bowl of water
Magnifying glass
Tissue paper
Construction paper
Clay
Flashlight
Tape
Scissors
Pen
(Touch or hover over each item for more information)

How To Make It

Artificial Eye 01 Artificial Eye 02 Artificial Eye 03 Artificial Eye 04 Artificial Eye 05 Artificial Eye 06 Artificial Eye 07

Things To Try

Move the flashlight up, down, left, and right as you continue to shine it through the magnifying glass towards the eyeball (goldfish bowl).  The image of your shape will form on different parts of the retina (tissue paper).

How It Works

The human eye [1] is an opaque ball that is filled with a water-like fluid called vitreous humor.  In your artificial eye, the goldfish bowl serves as the eyeball.

Like a camera, the eye focuses (or converges) incoming rays of light from a scene onto a light-sensitive surface so that it can be captured (and seen).  The light-sensitive surface inside a digital camera is called the image sensor (older cameras use rolls of film instead), but the light-sensitive surface on the back of the eye is called the retina.  In your artificial eye, the tissue paper serves as the retina, and the image that is formed on it can be clearly seen.

The squishy, gelatinous lens at the front of the eye refracts (or bends) the incoming light to focus it.  The magnifying glass acts as your artificial eye’s lens. Cameras also have lenses to focus light, but these lenses are usually made from a clear solid material like glass or plastic instead of a liquid or a gel.

Bigshot Connections

Fun Facts

Resolution of the Eye

The resolution (or level of detail that can be seen) of the human eye varies along different parts of the retina.  At the fovea, which is the part of the retina that lies in the center of one’s line of sight, the eye has a very fine resolution since light and color receptors (called rods and cones, respectively) are extremely packed.  Outside this point of gaze, however, the level of detail drops significantly, falling by half at just 2.3°from the line of sight, and falling by 90% at just 20° from the line of sight.

Iris Codes

Iris

The intricate pattern of the iris (the colored part of the front of an eye) is unique for each eye.  In fact, the iris is a much more reliable identifier for a person than fingerprints.  Iris patterns also stay much more consistent than fingerprints throughout a person's lifetime, resisting everyday wear and tear.  For these reasons, scientists are very interested in developing iris scanning technology to be used as a reliable way of identifying people.

Eye Shine

Eye shine on a raccoon

Many animal eyes have a layer of reflective tissue behind the retina that helps them see better in the dark, when they usually search for prey.   It acts as a mirror in order to reflect light back towards the retina, and is the reason why the eyes glow when they are caught in a beam of light.  This so-called "eye shine" is different from the "red eye" effect that is often seen in photos of people that were taken with a flash.  In that case, the red color is caused by blood in the tissues that are located behind the retina.

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ReferenceReferences

[1] Marieb, E. N. and Hoehn, K., Human Anatomy & Physiology. Benjamin Cummings, 2006
[2] "Iris recognition." Wikipedia, The Free Encyclopedia. [Online]. Available: http://en.wikipedia.org/wiki/Iris_recognition. [Accessed: Feb 13, 2010].
[3] Tapetum Lucidum." Wikipedia, The Free Encyclopedia. [Online]. Available: http://en.wikipedia.org/wiki/Tapetum_lucidum. [Accessed: Feb 13, 2010].
[4] N. Ardley, 101 great science experiments. DK Publishing, 2006
[5] B. A. Wandell, Foundations of vision. Sinauer Associates, 1995