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 a ray diagram for the correction of this defect.
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Solution
If a student cannot see the blackboard distance to her she is suffering from myopia.
Myopia is the inability of an eye in viewing long distant objects.
The image in this case is formed before the retina.
The short-sightedness is corrected by using a concave lens which diverges and shifts the image to the retina.
Hence, the doctor advises a concave lens of suitable focal length.