Question
Write a short note on "Myopia".
✓
Answer
A person with myopia can see nearby objects (i.e. objects at short distances) clearly but can not see distant objects (i.e. objects at large distances) clearly.
→ Myopia is also known as "near sightedness" or "short sightedness".
→ Far point of a myopic person is not at infinity but shorter than that, somewhere at few metres, say at point $O$ in fig. (a) given below.
$O=$ Far point of a myopic eye
$O^{\prime}=$ Far point of a normal eye
→ In a myopic eye, image of distant object is formed in front of retina, as shown in fig. (b). Since image is not formed on the retina, distant object is not seen clearly by such eye.
→ This defect arises due to (i) excessive curvature of eye-lens (with too short focal length) or (ii) bulky eyeball (elongated eyeball).
→ This defect can be corrected by using concave lens of suitable power, as shown in fig. (c) where the image is brought back on the retina, to see the distant object clearly.
→ Myopia is also known as "near sightedness" or "short sightedness".
→ Far point of a myopic person is not at infinity but shorter than that, somewhere at few metres, say at point $O$ in fig. (a) given below.
$O=$ Far point of a myopic eye
$O^{\prime}=$ Far point of a normal eye
→ In a myopic eye, image of distant object is formed in front of retina, as shown in fig. (b). Since image is not formed on the retina, distant object is not seen clearly by such eye.
→ This defect arises due to (i) excessive curvature of eye-lens (with too short focal length) or (ii) bulky eyeball (elongated eyeball).
→ This defect can be corrected by using concave lens of suitable power, as shown in fig. (c) where the image is brought back on the retina, to see the distant object clearly.
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