Human Eye & Light: 20 flashcards
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1. What is the main function of the cornea in the human eye?
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The cornea is the transparent front part that refracts (bends) light entering the eye, providing most of the eye's optical power.
2. What is the role of the iris?
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The iris controls the size of the pupil, regulating the amount of light entering the eye.
3. How does the pupil respond to bright light?
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The pupil constricts (becomes smaller) to reduce the amount of light entering the eye.
4. What is the function of the crystalline lens in the eye?
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The lens fine-tunes the focus of light onto the retina by changing its shape (accommodation).
5. What is the retina?
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The retina is the light-sensitive layer at the back of the eye containing rods and cones that convert light into electrical signals.
6. What are rods and cones?
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Rods are sensitive to dim light and help in night vision; cones are sensitive to bright light and enable colour vision.
7. What is the optic nerve's function?
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The optic nerve carries electrical signals from the retina to the brain for interpretation.
8. Define the power of accommodation of the eye.
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The ability of the eye's lens to change its focal length to focus on objects at different distances.
9. What is the near point of a normal human eye?
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The near point is about 25 cm, the closest distance at which the eye can focus clearly.
10. What is the far point of a normal human eye?
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The far point is infinity, the farthest distance the eye can see clearly without strain.
11. What is myopia?
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Myopia (nearsightedness) is a defect where distant objects appear blurry because the image forms in front of the retina.
12. What lens is used to correct myopia?
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A concave (diverging) lens is used to correct myopia.
13. What is hypermetropia?
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Hypermetropia (farsightedness) is a defect where nearby objects appear blurry because the image forms behind the retina.
14. What lens is used to correct hypermetropia?
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A convex (converging) lens is used to correct hypermetropia.
15. What is presbyopia?
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Presbyopia is an age-related condition where the eye's lens loses flexibility, making it hard to focus on close objects.
16. What is a cataract?
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A cataract is a clouding of the eye's lens, leading to blurred vision, often treated with surgery.
17. What is dispersion of light?
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Dispersion is the splitting of white light into its component colours (spectrum) when passing through a prism.
18. What causes the blue colour of the sky?
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The sky appears blue due to Rayleigh scattering, where shorter blue wavelengths are scattered more by air molecules.
19. Why does the Sun appear reddish at sunrise and sunset?
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At sunrise/sunset, light travels a longer path through the atmosphere, scattering blue light away and leaving red/orange light.
20. What is a rainbow?
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A rainbow is a natural spectrum formed by dispersion, refraction, and reflection of sunlight in water droplets.
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