The student is suffering from myopia, also known as nearsightedness. In this condition, the person is unable to see distant objects clearly while having a normal or relatively good vision for close objects.


There are two possible reasons for the student's myopia:
1. Elongated Eyeball: In a normal eye, light rays entering the eye converge at the retina, resulting in clear vision. However, in myopia, the eyeball is elongated, causing the light rays to converge in front of the retina instead of directly on it. As a result, the images formed on the retina are blurred, leading to difficulty in seeing distant objects clearly.
2. Increased Curvature of the Cornea: Another possible reason for myopia is an increased curvature of the cornea. This altered shape of the cornea causes light rays to bend more sharply, again resulting in the formation of an image in front of the retina.


Myopia can be corrected using concave lenses. These lenses are thinner at the center and thicker at the edges, causing the light rays to diverge before entering the eye. This divergence of light compensates for the excessive convergence caused by the elongated eyeball or increased corneal curvature, allowing the light rays to focus directly on the retina.


The power of the corrective lens required to correct myopia can be determined by the degree of nearsightedness. The power of the lens is measured in units called diopters (D), which indicate the focusing ability of the lens.

To calculate the power of the corrective lens, the reciprocal of the farthest point at which the student can see clearly is taken. In this case, the student is unable to see distinctly beyond 5 meters. Therefore, the power of the corrective lens can be calculated as follows:

Power of the lens = 1 / Farthest point of clear vision
= 1 / 5 meters
= 0.2 D

Therefore, the power of the corrective lens required for the student to see distant objects clearly is 0.2 diopters.