The human eye is like a camera. Its lens system forms an image on… - Vidyadip

Question

The human eye is like a camera. Its lens system forms an image on a light-sensitive screen called the retina. Light enters the eye through a thin membrane called the cornea. It forms the transparent bulge on the front surface of the eyeball as shown in the figure. The crystalline lens merely provides the finer adjustment of focal length required to focus objects at different distances on the retina. We find a structure called iris behind the cornea. Iris is a dark muscular diaphragm that controls the size of the pupil. The pupil regulates and controls the amount of light entering the eye.

There are mainly three common refractive defects of vision. These are (i) myopia or near-sightedness, (ii) hypermetropia or far-sightedness, and (iii) Presbyopia. These defects can be corrected by the use of suitable spherical lenses.
(i) What is the function of pupil in the human eye ?
(ii) What is the far point and near point of human eye with normal vision?
(iii) A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from?
(iv) What is the function of iris in human eye ?

✓

Answer

(i) The pupil regulates and controls the amount of light.
(ii) The far point is infinity and near point is about 25 $cm$ of the normal human eye.
(iii) The student is suffering from short-sightedness or myopia.
or
(iv) Iris is a dark muscular diaphragm that controls the size of the pupil.

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