1. Nearsightedness (Myopia):
- Nearsighted people can see nearby objects clearly, but objects farther away appear blurry.
- Corrective lenses for nearsightedness are called concave lenses or diverging lenses.
- Concave lenses are thinner at the center and thicker at the edges.
- When light rays enter a concave lens, they diverge (spread out) before reaching the eye.
- This divergence of light rays causes the focal point (where the light rays converge) to be in front of the retina.
- As a result, the image of distant objects is projected onto the retina, allowing nearsighted individuals to see faraway objects clearly.
2. Farsightedness (Hyperopia):
- Farsighted people have difficulty seeing objects close to them, but they can see distant objects clearly.
- Corrective lenses for farsightedness are called convex lenses or converging lenses.
- Convex lenses are thicker at the center and thinner at the edges.
- When light rays enter a convex lens, they converge (come together) before reaching the eye.
- This convergence of light rays causes the focal point to be behind the retina.
- As a result, the image of nearby objects is projected onto the retina, allowing farsighted individuals to see close objects clearly.
3. Astigmatism:
- Astigmatism is a common vision problem caused by an irregularly shaped cornea or lens.
- Corrective lenses for astigmatism are called cylindrical lenses or toric lenses.
- Cylindrical lenses have a curved surface in one direction and a flat surface in the perpendicular direction.
- They are designed to correct the uneven curvature of the cornea or lens, allowing individuals with astigmatism to see objects clearly at all distances.
Corrective lenses work by manipulating the way light rays enter the eye, altering the focal point of the light, and ensuring that the images of objects are focused correctly on the retina. This allows people with vision problems to see clearly and comfortably.
