Nearsightedness (Myopia) / Farsightedness (Hyperopa) - Betzold 89947 Handbuch

Table of Contents
1. Nearsightedness (Myopia) / Farsightedness (Hyperopa) ...................................................................................... p. 18
2. Introduction on the Subject of Eyeglasses ............................................................................................................ p. 21
3. Excursion Optical Lenses ...................................................................................................................................... p. 21
4. Interesting facts on the topic of eyeglasses............................................................................................................ p. 21
5. Experimenting with LED spotlights, lenses and activity cards................................................................................ from p. 22
5. 1 Experiment "converging or diverging lens?"......................................................................................... p. 22
5. 2 Experiment "light refraction"................................................................................................................. p. 22
5. 3 Experiment "defective vision I"............................................................................................................. p. 22
5. 4 Experiment "defective vision II"............................................................................................................ p. 22
5. 5 Experiment "accommodation".............................................................................................................. p. 23
5. 6 Experiment "image-formation on the retina"......................................................................................... p. 23
6. Solutions................................................................................................................................................................. from p. 23
to Experiment 5.1....................................................................................................................................... p. 23
to Experiment 5.2....................................................................................................................................... p. 24
to Experiment 5.3....................................................................................................................................... p. 24
to Experiment 5.4....................................................................................................................................... p. 24
to Experiment 5.5....................................................................................................................................... p. 25
to Experiment 5.6....................................................................................................................................... p. 25
7. Fill in the blanks...................................................................................................................................................... from p. 25
8. Copy Templates...................................................................................................................................................... from p. 27
Contents
7 optical lenses
1. What is nearsightedness (myopia), what is farsightedness (hyperopia) ?
Images must be formed exactly on the retina for an object to be seen clearly. The focal point of parallel incident rays must there-
fore lie precisely on the retina.
Illustration 1: Normal eye with focal point on the retina
Nearsightedness is a visual defect in which the length of the eyeball is not in proportion to the focusing power of the eye. Either
the eyeball is too long or the refractive power is too strong. Incoming light rays focus at a point in front of the retina. Nearsighted
persons are able to see close-up objects well, but have difficulty seeing in the distance.
Nearsightedness occurs when the eyeball is too long (common) or the refractive power of the eye's lens is too strong (rare). The
position of the focal point falls to the front. This means that objects in the distance cannot be focused clearly, whereas nearby
objects can. Even items that are so close to the eye that a person with normal vision cannot focus clearly, can still be seen very
well by a nearsighted person.
18
1 LED spotlight 4 activity cards 1 manual
© Arnulf Betzold GmbH