What is hypermetropia? State the two causes of hypermetropia. With the help of ray diagrams, show
(a) the eye-defect hypermetropia
(b) correction of hypermetropia by using a lens
Answers
Answer:
Hypermetropia is a defect of vision in which a person can see distant objects clearly and distinctively, but is not able to see nearby objects comfortably and clearly.
Hypermetropia is caused due to
reduction in the curvature of the lens
decrease in the size of the eyeball
Since a convex lens has the ability to converge incoming rays, it can be used to correct this defect of vision.
Hope this information will clear your doubt regarding defects of vision.
Hypermeteropia, is also known as long sightedness, occurs due to the shortening of eye ball. With the defect, distance objects can be seen clearly but nearby objects cannot be seen clearly. The focal length of eye lens is increased or the distance between eye lens and retina decreases. Hence, the near point will not be at 25 cm for such eyes and the near point has moved farther. Due to this, the image of nearby objects are formed behind the retina.
(a) Let a person with hypermeteropia eye
can see objects beyond a distance 'd'.
Suppose that he wants to see all objects
closer than this distance up to a Distance
'D'. Then the focal length of the required
convex lens is,
f = dD / d - D
(b) This defect can be corrected using convex lens.
Note : Refer the attachment.
