Give short note on Defects of Vision and explanation
Please answer it fast!
Answers
Answer:
Defects of vision is the loss of power of accommodation of the human eye. They are mainly of three types: Myopia/ near-sightedness: The person can see nearby objects clearly but is unable to see objects beyond some distance. For such a person, far point changes to infinity to some finite distance.
Defects of vision is the loss of power of accommodation of the human eye. They are mainly of three types:
Myopia/ near-sightedness: The person can see nearby objects clearly but is unable to see objects beyond some distance. For such a person, far point changes to infinity to some finite distance.
Hypermetropia/ far-sightedness: The person can see far objects clearly but is unable to see nearby objects clearly. For such a person, near point increases to a distance greater than 25 cm. It is corrected with the help of a convex lens. The power of the lens is set so that the image of an object kept at 25 cm from the lens is formed at near-point of the eye.
Presbyopia: This defect is common in old-people and is caused by the weakening of ciliary muscles. In this defect, both the near-point and the far-point are affected. It is corrected with the help of a bifocal length which is a combination of convex lens and a concave lens.