The Human Eye


  • The human eye is one of the most valuable and sensitive sense organs. It enables us to see the wonderful world and the colours around us.
  • Retina: The human eye is like a camera. Its lens system forms an image on a light-sensitive screen called the retina.
  • Cornea: Light enters the eye through a thin membrane called the cornea.
  • Eye Ball: It forms the transparent bulge on the front surface of the eyeball as shown in figure. The eyeball is approximately spherical in shape with a diameter of about 2.3 cm
  • Iris: Iris is a dark muscular diaphragm that controls the size of the pupil. The pupil regulates and controls the amount of light
  • Function of Iris: Most of the refraction for the light rays entering the eye occurs at the outer surface of the cornea. 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.
  • The eye lens forms an inverted real image of the object on the retina. The retina is a delicate membrane having enormous number of light-sensitive cells.
  • The light-sensitive cells get activated upon illumination and generate electrical signals. These signals are sent to the brain via the optic nerves. The brain interprets these signals, and finally, processes the information so that we perceive objects as they are.