Question

Which defect of the eye is known as far- sightedness? When does this defect arise ? State two reasons. How is this defect corrected ?

Answer 1

Answer:

far sightness is known as hypermetropia. A person with this problem has difficulty in seeing nearby objects but can see distant object clearly .This problem arises when the the rays form the image behind the retina.This is caused because of the elongation of focal length or when the eyeball gets smaller in size. It is corrected by concave lens of suitable focal length

hope this will help you

Answer 2

Answer:

Hypermetropia isa defect of the eye that known as far sightedness.

This defect arises when:-

1) a person can't see the nearby objects clearly but can see the distant objects clearly.

2) eye lens become low converging power & eye ball being too short.

Hypermetropia (far sightedness) is corrected by using spectacles containing convex lens. It explained as follows:-

When convex lens of suitable power is placed in front of the hypermetropic eye, then the diverging rays of light coming from the nearby object(at 25cm) are first converged by this convex lens. Due to this, convex lens forms a virtual image of the nearby object.

Please note that "Convex lens used for correcting hypermetropia (far sightedness) should be of such a focal length that it forms a virtual image of the object, at the near point of the hypermetropic eye."