$A$ student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?

A student who has difficulty reading the blackboard while sitting in the last row is unable to see distant objects clearly. This condition is known as $Myopia$ (near-sightedness). In this defect, the image of a distant object is formed in front of the retina rather than on the retina itself. This defect can be corrected by using a concave lens of suitable focal length, which diverges the light rays before they enter the eye, allowing the image to be focused correctly on the retina.