When do we consider a person to be myopic or hypermetropic? Explain using diagrams how the defects associated with myopic and hypermetropic eyes can be corrected?
Explanation:-
Myopia - short-sightedness.
A person with myopia can see nearby objects clearly.
Light from a distant object forms an image before it reaches the retina
This is because the eye is too long or the cornea or crystalline lens is too short.
To correct this defects a concave lens is placed in front of a myopic eye, moving the image back to the retina and clarifying the image as shown below:
Hypermetropia - far-sightedness.
A person with hypermetropia can see distant objects clearly.
An image of a nearby object is formed behind the retina.
This is because the eye is too short or the cornea or crystalline lens does not refract the light enough.
To correct this defect, a convex lens is placed in front of a hypermetropic eye.
The image is moved forward and focuses correctly on the retina.