Q19 of 25 Page 94

Which part of the eye gets affected if someone is suffering from cataract? How is it treated?

The lens of the eyes gets affected if someone is suffering from cataract. If this happens the eyesight becomes foggy which is due to the reason that the lens becomes cloudy.

Cataract is treated by removing the opaque lens from the eye and then inserting a new artificial lens in its place.


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Eyes of the nocturnal birds have large cornea and a large pupil. How does this structure help them?

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What kind of lens is there in our eyes? Where does it form the image of an object?

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Boojho planned an activity to observe an object A through pipes as shown in Fig. 16.8, so that he could see objects which he could not directly see.


(a) How many mirrors should he use to see the objects?


(b) Indicate the positions of the mirrors in the figure.


(c) What must be the angle with respect to the incident light at which he should place the mirrors?


(d) Indicate the direction of rays in the figure.


(e) If any of the mirrors is removed, will he be able to see the objects?


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There is a mistake in each of the following ray diagrams given as Fig. 16.9 a, b, and c. Make the necessary correction (s).