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Science · Textbook solutions

The Human Eye and the Colourful World

Every solved example, exercise, and miscellaneous question — in the order the textbook teaches them. · 16 questions

10.2 Defects of Vision and their Correction

4 q

Questions

Practice · 4
  1. IT 10.1 Q1
    What is meant by power of accommodation of the eye?
  2. IT 10.1 Q2
    A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?
  3. IT 10.1 Q3
    What is the far point and near point of the human eye with normal vision?
  4. IT 10.1 Q4
    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?

Exercises

12 q
  1. Ex 10 Q1
    The human eye can focus on objects at different distances by adjusting the focal length of the eye lens. This is due to
    1. A.
      presbyopia.
    2. B.
      accommodation.
    3. C.
      near-sightedness.
    4. D.
      far-sightedness.
  2. Ex 10 Q2
    The human eye forms the image of an object at its
    1. A.
      cornea.
    2. B.
      iris.
    3. C.
      pupil.
    4. D.
      retina.
  3. Ex 10 Q3
    The least distance of distinct vision for a young adult with normal vision is about
    1. A.
      25 m.
    2. B.
      2.5 cm.
    3. C.
      25 cm.
    4. D.
      2.5 m.
  4. Ex 10 Q4
    The change in focal length of an eye lens is caused by the action of the
    1. A.
      pupil.
    2. B.
      retina.
    3. C.
      ciliary muscles.
    4. D.
      iris.
  5. Ex 10 Q5
    A person needs a lens of power −5.5-5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5+1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?
  6. Ex 10 Q6
    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?
  7. Ex 10 Q7
    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 the near point of the normal eye is 25 cm.
  8. Ex 10 Q8
    Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
  9. Ex 10 Q9
    What happens to the image distance in the eye when we increase the distance of an object from the eye?
  10. Ex 10 Q10
    Why do stars twinkle?
  11. Ex 10 Q11
    Explain why the planets do not twinkle.
  12. Ex 10 Q12
    Why does the sky appear dark instead of blue to an astronaut?