Why is convex lens used for myopia?

A convex lens is not used for correcting myopia. In fact, a concave lens is used to correct myopia. Here's why:

1. Myopia, also known as nearsightedness, is a condition where distant objects appear blurry while nearby objects are seen clearly. This occurs because the shape of the eyeball is elongated, causing light rays to focus in front of the retina instead of on it.

2. To correct myopia, we need to diverge the incoming light rays so that they focus on the retina. A concave lens, also known as a diverging lens, achieves this by bending the light rays outward.

3. When a concave lens is placed in front of the eye, it diverges the incoming light rays, causing them to focus farther back on the retina. This allows people with myopia to see distant objects more clearly.

4. Convex lenses, on the other hand, are converging lenses that converge light rays toward a focal point. They are used for correcting hyperopia (farsightedness), where distant objects are seen clearly but nearby objects appear blurry.

Therefore, a concave lens, not a convex lens, is used for correcting myopia. This is because concave lenses diverge light rays, which is what is needed to correct the focusing issue caused by myopia.