Question

Myopia occurs due to:
A. Increase in the focal length of the eye lens
B. Decrease in the distance between retina and lens
C. Decrease in the focal length of the eye lens
D. Increase in the distance between retina and lens

Answer 1

Hint: Short-sightedness which is additionally referred to as myopia is caused when the eyeballs get elongated. can be corrected by using a diverging or concave lens of appropriate power.

Complete step-by-step solution:
The person who is suffering from myopia can see nearby objects clearly but cannot see distant objects distinctly. A person who is suffering from this defect has a far point nearer than infinity. Such a person would only be able to see clearly up to a distance of a few meters. In a myopic eye a distant object’s image is formed in front of the retina and not at the retina itself.
This defect occurs either because of (i) excessive curvature of the eye lens, or (ii) elongation of the eyeball, or (iii) decrease in focal length of the eye lens. This defect can be corrected by using a diverging or concave lens of appropriate power.
Hence, option (C) is the correct answer.

Note: The normal vision of an eye is from 25cm to infinity. But in some situations, the eye is unable to focus the image of the object on the retina, so in such cases, the person is said to suffer from eye defect. Defects other than myopia are hypermetropia and presbyopia. Hypermetropia is also known as long-sightedness is caused when the eyeball is too short or when the focal length of the eye lens is too long. Presbyopia is caused when the eye loses its power of accommodation. It occurs because of aging due to the weakening of the ciliary muscles and diminishing flexibility of the eye lens.