PURPOSE: Demonstrate the optics of the eye and corrections of optical defects.
DESCRIPTION: The eye model is an oval tank, filled with water representing the aqueous humor, with a lens representing the eye lens on one end and a screen representing the retina with three positions: normal, nearsighted, and farsighted.
The eye lens focuses light from a distant object onto the retina, which is positioned in the center of three retinal locations. The image on the retina can be seen to be inverted by the eye lens. If the retina is moved to the far position, the eye is too long, producing nearsighted vision. This can be corrected using a diverging lens as the eyeglass. If the retina is moved to the near position, the eye is too short, producing farsighted vision. This can be corrected by using a converging lens eyeglass. Instruction sheet, including list of corrective lenses and positions for various optical elements is with the eye model.
The photograph at the right above shows the retina in its farsighted position (too close), the eye lens just inside the water bath on the right, with the object focused by a corrective convex eyeglass lens in front of (just outside) the eye.
Television can be used to make the action visible to a large group.
The pictures below show the image on the retina for an initially focused eye, a farsighted eye, the corrected farsighted eye, a nearsighted eye, and the corrected nearsighted eye.
SUGGESTIONS: Click here for a PDF version of
the article "Simple Experiments on the Physics of Vision," by Adolf Cortel Ortuno
(English translation of the article in
See Question
of the Week #285 and #286
for information on using this demonstration to enhance class involvement.
REFERENCES: (PIRA 6J10.21)
EQUIPMENT: Eye model filled with water, set of lenses, light source with object cross, and instructions, with TV system.
SETUP TIME: 5 min.
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