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Question
A student sitting at the back of the classroom cannot read clearly the letters written on the blackboard. What advice will a doctor give to her? Draw ray diagram for the correction of this defect.
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Solution
Since, the student sitting at the back of the classroom cannot read clearly the letters written on the blackboard, it means the student is suffering from Myopia. The doctor will suggest her, a concave lens of suitable power which will bring the image back on retina and therefore the defect will be corrected.
The ray diagram for the correction of this defect is as below :

Correction for Myopia
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