Question 116 of 782

The parts of the mammalian eye that strongly bend light rays are the

  • A. cornea and the lens
  • B. cornea and aqueous humour
  • C. cornea and vitreous humour
  • D. lens and aqueous humour

Correct Answer: A

Explanation
The correct option is A. cornea and the lens. Detailed Explanation:
  1. Understanding Light Refraction in the Eye:
  2. The eye functions by bending (refracting) light rays to focus them onto the retina, which is the light-sensitive layer at the back of the eye. The ability to bend light is crucial for clear vision.
  3. Role of the Cornea:
  4. The cornea is the transparent front part of the eye. It has a curved shape, which allows it to bend light rays as they enter the eye. The cornea is responsible for about 70% of the eye's total refractive power. Its curvature and the difference in refractive index between air and the corneal tissue cause significant bending of light.
  5. Role of the Lens:
  6. The lens is located behind the iris and the pupil. It is flexible and can change shape (become thicker or thinner) to adjust the focus of light rays onto the retina. This process is known as accommodation. The lens contributes about 30% of the eye's total refractive power. Its ability to change shape allows the eye to focus on objects at various distances.
  7. Why Other Options Are Incorrect:
  8. B. cornea and aqueous humour: The aqueous humour is the clear fluid in the front part of the eye, between the cornea and the lens. While it plays a role in maintaining intraocular pressure and providing nutrients, it does not significantly bend light rays. Therefore, this option is incorrect.
  9. C. cornea and vitreous humour: The vitreous humour is the gel-like substance filling the space between the lens and the retina. Similar to the aqueous humour, it does not have a significant refractive index difference that would cause it to bend light rays. Thus, this option is also incorrect.
  10. D. lens and aqueous humour: While the lens does bend light, the aqueous humour does not contribute to this process. As mentioned earlier, it primarily serves other functions in the eye. Therefore, this option is incorrect as well.
Summary of Key Points:
  • The cornea and lens are the primary structures in the eye that bend light rays to focus them on the retina.
  • The cornea provides the majority of the eye's refractive power due to its curved shape.
  • The lens adjusts its shape to fine-tune focus for objects at varying distances.
  • The aqueous and vitreous humours do not significantly contribute to light refraction.
Revision Summary:
  • The cornea and lens are crucial for bending light in the eye.
  • The cornea accounts for about 70% of the eye's refractive power.
  • The lens adjusts its shape for focusing on near and far objects.
  • Aqueous and vitreous humours do not significantly bend light.
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