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Difficulty: MediumThin Lenses, Optical Instruments, and Defects of Vision

Match each eye defect to its corresponding optical cause and method of vision correction.

  • Myopia (Short-sightedness)Image forms in front of the retina due to an elongated eyeball; corrected using a concave (diverging) lens.
  • Hypermetropia (Long-sightedness)Image forms behind the retina due to a shortened eyeball; corrected using a convex (converging) lens.
  • AstigmatismUnequal curvature of the cornea or lens causing light in different planes to focus at different points; corrected using a cylindrical lens.
  • PresbyopiaLoss of accommodation power due to aging and hardening of the crystalline lens; corrected using bifocal lenses.

Answer

Myopia corresponds to image formation in front of the retina (corrected with a concave lens); Hypermetropia corresponds to image formation behind the retina (corrected with a convex lens); Astigmatism corresponds to uneven corneal curvature (corrected with a cylindrical lens); Presbyopia corresponds to age-related loss of accommodation (corrected with bifocal lenses).
Each vision defect is matched precisely to its biological cause and optical correction method: Myopia with image in front of retina and concave lens, Hypermetropia with image behind retina and convex lens, Astigmatism with non-spherical cornea and cylindrical lens, and Presbyopia with age-related loss of accommodation and bifocal lenses.

Step-by-Step Solution

1
Identify the cause and corrective lens for Myopia.
Myopia causes light to focus in front of the retina due to excessive converging power or an elongated eyeball, requiring a concave (diverging) lens.
A concave lens diverges incoming light rays prior to entry into the eye so the focal point moves back to the retina.
2
Identify the cause and corrective lens for Hypermetropia.
Hypermetropia causes light to focus behind the retina due to insufficient converging power or a shortened eyeball, requiring a convex (converging) lens.
A convex lens provides extra converging power to bring the focal point forward onto the retina.
3
Identify the cause and corrective lens for Astigmatism.
Astigmatism arises from irregular corneal curvature, requiring a cylindrical lens.
Cylindrical lenses vary focal power along a specific axis to equalize uneven light refraction.
4
Identify the cause and corrective lens for Presbyopia.
Presbyopia is caused by loss of elasticity in the lens with age, requiring bifocal lenses.
Bifocal lenses provide dual correction zones for distance and near vision.

Key Concept

Vision Defects and Lens Corrections
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Topics

Thin Lenses, Optical Instruments, and Defects of Vision

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