You can tell whether people are nearsighted or farsighted by looking at the width of their face through their glasses. If a person's face appears narrower through the glasses (Fig. 25-47), is the person farsighted or nearsighted? Try to explain, but also check experimentally with friends who wear glasses.
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Lens thicker at the Centre than at the edges is a converging lens. Lens thinner at the Centre than at the edges is a diverging lens. A diverging lens always forms a virtual image that will be upright and smaller than the object, regardless of the position of the object.
Normal eye focuses light and produces a sharp image, just like a camera. The cornea-lens system focuses light onto the back surface of the eye called retina. A person, who can see distant objects clearly but cannot focus on near objects is farsighted. Farsightedness is corrected with a converging lens. A person, who can see near objects clearly but cannot focus on distant objects is nearsighted and is corrected with a diverging lens.