Learn Science [Form 2]

Chapter 1 - Lesson 7 part 2

CHAPTER 1: THE WORLD THROUGH OUR SENSES

1.7 Light and Sight

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ACTIVITY 1.5 : Explaining short-sightedness and long-sightedness and ways of correcting them

Figure 1.28

Procedure
1 A model of the eye is set up. The round-bottomed flask filled with water containing a little fluorescein represents an eyeball.
2 A thicker convex lens is affixed to the flask A.
3 A light beam from a light source is directed onto the lens (Figure 1.28 (a)). 
4 The light beam that passes through the thicker lens forms an image inside the flask. This shows short-sightedness. 
5 A concave lens is positioned in front of the lens. Observe what happens.
6 A thinner convex lens is affixed to the round-bottomed flask B as shown in Figure 1.28 (b).
7 Steps 3 to 5 are repeated for flask B by using a convex lens.

Observation

Figure 1. 29

Conclusion
Short-sightedness can be corrected by using a concave lens and long-sightedness can be corrected by using a convex lens.

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3 Comparison between long-sightedness and short-sightedness.