Structure of human eye

Structure of Human Eye

• Eyeball: In human eye, eyeball is the round part with approximate diameter of 2.3 cm.
• Cornea: It is transparent, thin membranous, bulged structure present in front of eye. When light falls on eye, rays of light gets reflected through cornea, in such a way that light falls on lens of the eye.
• Crystalline Lens: Lens present in eye is in nature. Light rays fall from cornea on the lens. From lens, light rays are further refracted to fall on retina. In addition to this, lens also provides finer adjustments in focal length to form a clear image on retina. Image formed on retina is real and inverted.
• Pupil: Part of human eye which appears dark is pupil. It regulates and controls amount of light entering in the eye.
• Iris: It is the dark muscular diaphragm that control size of pupil. In case of bright light, it contracts pupil, thereby allowing less light to fall on eye. However, in case of dim light it expands pupil, allowing more light to fall on eye.
• Retina: Retina is delicate light sensitive screen of human eye. It consist of light sensitive cells that generate electrical impulses when exposed to light.
• Optic nerves: Optic nerves are the nerve fibres that sends signals of light sensitive cells to the brain.

Power of Accommodation of Human eye

Human eye can see distant as well as near objects clearly. It is possible due to power of accommodation.

“Ability of eye to adjust its focal length is called power of accommodation.”

Vision of Distant Objects

While seeing the distant objects, ciliary muscle get relaxed, due to which curvature of eye decreases, hence, lens becomes thin which increases focal length, thereby allowing the distant vision. However, eye can see objects clearly upto maximum distance. This is known as far point of eye. Far point for normal human eye is infinity.

Vision of closer objects

While seeing the closer object, ciliary muscle in human eye get contracted, due to which curvature of eye increases, hence, lens becomes thick which decreases the focal length, thereby allowing vision to closer objects. However, eye can see clearly upto minimum distance called nearpoint of eye. For normal human eye near point is 25 cm in adults.

This article is helpful for Class 10 Science

Keywords: Structure of human eye, Crystalline lens, Far point of eye, Near point of eye

Related articles

Structure and Functions of Plasma Membrane in a Cell
Cell Organelle and their Functions
Meristematic Tissue in Plants
Working of Human Digestive System
The Process of Photosynthesis