Q19 of 216 Page 456

(i) What is myopia? State the two causes of myopia. With the help of labelled ray diagrams show

(a) The eye defect myopia


(b) Correction of myopia using a lens.


(ii) Why is the normal eye unable to focus on an object placed within 10 cm from the eye?

(i) Myopia or near sightedness where a person can see the objects near to him but cannot see farther objects distinctly.


CAUSES: 1. Decreases in focal length of the eye lens.


2. Elongation of the eyeball.



(ii) Human eye lens tends to adjust the focal length he/she can see this is called accommodation of eye lens. This accommodation lies between 25cm to infinity.


A person can’t focus at 10cm because it lies outside the range of accommodation and focusing on this length may have bad impact on eyes that is a strain.


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