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

Match each defect of vision to its correct image formation characteristic and mode of optical correction.

  • Hypermetropia (Long-sightedness)Light rays focus behind the retina; corrected using a converging (convex) lens.
  • Myopia (Short-sightedness)Light rays focus in front of the retina; corrected using a diverging (concave) lens.
  • PresbyopiaLoss of accommodation due to aging ciliary muscles; corrected using converging or bifocal lenses.
  • AstigmatismUnequal curvature of the cornea or lens in different planes; corrected using a cylindrical lens.

Answer

Hypermetropia pairs with light focusing behind the retina (corrected with a converging lens). Myopia pairs with light focusing in front of the retina (corrected with a diverging lens). Presbyopia pairs with age-related loss of accommodation (corrected with bifocal/converging lenses). Astigmatism pairs with unequal corneal curvature in different planes (corrected with a cylindrical lens).
Each vision defect uniquely corresponds to a specific optical fault and corrective lens: Hypermetropia focuses images behind the retina (convex lens), Myopia focuses images in front of the retina (concave lens), Presbyopia involves age-related elasticity loss (bifocal/convex lens), and Astigmatism stems from asymmetric corneal curvature (cylindrical lens).

Step-by-Step Solution

1
Identify the structural defect and focus point for Hypermetropia.
Near point moves farther away, so light rays from standard near point focus behind the retina. A converging (convex) lens is required to bend light rays inward prior to entering the eye.
Hypermetropic eyes lack sufficient refractive power for near vision.
2
Identify the structural defect and focus point for Myopia.
Far point is reduced, so light rays from distant objects focus in front of the retina. A diverging (concave) lens is required to diverge incoming parallel rays.
Myopic eyes possess excessive refractive power or an elongated eyeball.
3
Identify the cause and correction for Presbyopia.
Caused by aging of ciliary muscles and hardening of the eye lens. Corrected with converging or bifocal lenses.
Presbyopia specifically relates to loss of elastic accommodation in older individuals.
4
Identify the cause and correction for Astigmatism.
Caused by non-uniform curvature of the cornea along horizontal vs vertical axes. Corrected using cylindrical lenses.
Cylindrical lenses compensate for asymmetrical focal lengths along specific axes.

Key Concept

Defects of Vision and Corrective Lenses
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Topics

Thin Lenses, Optical Instruments, and Defects of Vision

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