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Construction of Human Eye

Human Eye. Construction of Human Eye iris, pupil, cornea, aqueous humour, lens, ciliary muscle, vitreous humour, retina Focusing seeing near object ( near point ) seeing distant object ( far point ) Eye defects Short-sight Long-sight. Construction of human eye. Retina. eye lens. iris.

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Construction of Human Eye

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  1. Human Eye • Construction of Human Eye • iris, pupil, cornea, aqueous humour, lens, ciliary muscle, vitreous humour, retina • Focusing • seeing near object ( near point ) • seeing distant object ( far point ) • Eye defects • Short-sight • Long-sight

  2. Construction of human eye Retina eye lens iris Cornea pupil Blind spot Ciliary muscles Vitreous humour

  3. Formation of image • Light entering the eye is refracted successively at the cornea, the aqueous humour, the lens and the vitreous humour. • The image is formed on the retina and the retina sends signal along the optical nerve to the brain, causing the sensation of sight. • The image formed on the retina is inverted but is interpreted as erect.

  4. Focusing near object Light from near object

  5. Focusing far away object Light from far away object

  6. Accommodation

  7. The average normal eye can focus objects easily from about 25 cm, i.e., the near point, to infinity, i.e. the far point. This range of distance of clear vision varies from one person to another and decreases with age. Near Point and Far Point

  8. Short sight Light from distant object

  9. Causes of short sight • The eyeball is a bit too long. • The lens lacks the ability to accommodate for a distant object.

  10. Diverging lens ( Concave lens ) Correction of short sight Light from distant object

  11. Long sight Light from near object

  12. Causes of long sight • The eyeball is a bit too short. • The lens lacks the ability to accommodate for a near object.

  13. Converging lens ( Convex lens ) Correction of long sight Light from near object

  14. Summary

  15. 1. Which of the following statements about the lens is/are correct ? Class Practice (1) The image formed on the retina is real. (2) The pupil is smaller in bright light than in dim light. (3) When the object distance changes, the eye focuses an object by chaning the focal length of the eye lens.

  16. 2. The near point of a long-sighted eye is 50 cm from the eye. A lens is used for correction. (a) What type of lens should be used ? (b) Find the focal length of the lens. Class Practice

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