Myopia

1. State that nearby objects are clear but distant objects are blurred. 2. Mention that the image forms in front of the retina. 3. Give possible cause: long eyeball or excessive lens power. 4. Say that a concave lens is used. 5. Explain that the lens diverges rays so the image moves to the retina.

Draw a myopic eye with parallel rays focusing before the retina, and then show a concave lens making the rays diverge before entering the eye.

A common wrong answer is to choose a convex lens. That is wrong because a convex lens would increase convergence and make the distant image form even earlier.

Myopia is a defect in which a person sees nearby objects clearly but distant objects appear blurred.

Myopia is a defect in which a person sees nearby objects clearly but distant objects appear blurred. Myopia correction uses a concave lens of suitable focal length to reduce the eye's converging power. A student can read a book easily but cannot clearly see the school notice board from the back row.

In myopia, light from a distant object is focused in front of the retina instead of on it. This can happen because the eyeball is too long or the eye lens has too much converging power. A concave lens is used for correction because it spreads the rays slightly before they enter the eye. Myopia correction uses a concave lens of suitable focal length to reduce the eye's converging power. If a student cannot see objects beyond 2 m clearly, the far point of the eye is 2 m. A concave lens is chosen so distant rays are diverged and the final image forms on the retina. Explain the defect, identify the lens used for correction, or draw a ray diagram showing the corrected image position. A common wrong answer is to choose a convex lens. That is wrong because a convex lens would increase convergence and make the distant image form even earlier.