Question

Explain giving reason the type of lens used to correct the defect of vision hypermetropia

Answer 1

Hypermetropia or longsightedness is that defect of vision due to which a person cannot see the nearby objects clearly though he can see the distant object clearly.
THE DEFECT OF EYE CALLED HYPERMETROPIA IS CAUSED DUE TO:
1.Due to larger focal length.
2. Due to eye ball too short.
So the image of nearby object falls behind the retina.
CORRECTION:
This eye defect can be corrected by using spectacles containing convex lenses.
When convex lens of suitable power is placed in front of Hypermetropia eye , then diverging rays of light coming from nearby object are first converged by convex lens.Due to this convex lens forms virtual image of nearby object.
Since rays of light now appear to come from this eye' s near point, they can be easily focused on retina.

Answer 2

The defect is caused due to the larger focal length and if the eyeball of an eye is too short then the defect of vision of hypermetropia results.
If some object is near the eye it will go directly behind the retina.
So for such errors, spectacles of a convex lens are used. So the rays which enter the eye first go through the convex lens and it forms a virtual image of the nearby objects which are easy to be focused on the retina.