A student has difficulty in reading the blackboard while sitting in last row. What could be defect of vision? Draw ray diagrams to illustrate this defect and its correction.

The student is suffering from myopia.

Myopia: It is the defect of the eye because of which distant objects cannot be seen clearly. Image is formed in front of the retina. It is also called Nearsightedness.

Cause: This defect of vision occurs when the eyeball slightly elongates from front to back. This causes light rays to focus at a point in front of the retina, rather than directly on its surface.

Remedy: It can be corrected by an appropriate concave lens.