Human Eye and Colourful World
1. What is meant by power of accommodation of eye?
2. A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the corrective lens used to restore proper vision?
3. What is the far point and near point of the human eye with normal vision?
4. A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?
5. The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to
(a) Presbyopia (b) Accommodation
(c) Near-sightedness (d) Far-sightedness
6. The human eye forms the image of an object at its
(a) Cornea (b) Iris
(c) Pupil (d) Retina
7. The least distance of distinct vision for an eye lens is caused by the action of the
(a) 25 m (b) 2.5 cm
(c) 25 cm (d) 2.5 m
8. The change in focal length of an eye lens is caused by the action of the
(a) Pupil (b) Retina
(c) Cilliary muscles (d) iris
9. A person needs a lens of power -5.5 dioptre for correcting his distinct vision. For correcting his near vision he needs a lens +1.5 dioptre. What is the focal length of the lens required for correcting (i) distinct vision, and (ii) near vision?
10. The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
11. Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct this defect? Assume that near point of the normal eye is 25 cm.
12. Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
13. What happen to the image distance in the eye when we increase the distance of an object from the eye?
14. Why do stars twinkle?
15. Explain why the planets do not twinkle.
16. Why does the Sun appear reddish early in the morning?
17. Why does the sky appear dark instead of blue to astronaut?