Q32 of 234 Page 279

Fill in the following blanks with suitable words:

A person is short-sighted if his eyeball is too ______ Spectacles with a ______ lens are needed. A person is long-sighted if his eyeball is too ______ Spectacles with a ______ lens are needed. These focus light rays exactly on to the ______

A person is short-sighted if his eyeball is too long Spectacles with a concave lens are needed. A person is long-sighted if his eyeball is too short. Spectacles with a convex lens are needed. These focus light rays exactly on to the retina.


More from this chapter

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30

What is presbyopia? Write two causes of this defect. Name the type of lens which can be used to correct presbyopia.

 31

When is a person said to have developed cataract in his eye ? How is the vision of a person having cataract restored?

 33

What is short-sightedness ? State the two causes of short-sightedness (or myopia). With the help of ray diagrams, show:

(i) the eye-defect short-sightedness.


(ii) correction of short-sightedness by using a lens.

 33

A person having short-sight cannot see objects clearly beyond a distance of 1.5 m. What would be the nature and power of the corrective lens to restore proper vision?