Physics > Human eye

Explore structure and function of the human eye: iris, cornea, pupil and retina. Find out the viewing angle of the human eye and how much light it is picking up.

Human eye – an organ that reacts to and perceives light, creating color vision and depth perception.

Learning challenge

  • Understand the parts of the eye and their functions.

Key points

  • The eye is represented by several parts, including the iris, cornea, pupil and retina.
  • The eye contains 6 muscles responsible for movement, tension and torque.
  • The eye functions like a camera.


  • Aperture is the diameter of the hole that limits the width of the light path throughout the system.
  • The pupil is the opening in the center of the iris through which light passes and focuses on the retina.

The human eye refers to one of the 5 senses. It is an organ that interacts with light. With its help, we are able to perceive light, color and depth. The standard eye is capable of recognizing up to 10 million different colors.


Let’s take a close look at the structure and function of the human eye. The eye is not an ideal sphere and is represented by two main parts: the cornea and the sclera. They are united by a ring – a limbus. The visible part is the iris, in the center of which is the pupil. This is a black dot that changes size depending on focus. These elements are covered by a transparent cornea. The fundus of the eye is located opposite the pupil, but it is inside and cannot be seen without special tools. Signals to the brain are transmitted along the optic nerve. The eye consists of three layers:

The cornea and lens function together to create a real image on the light-sensitive retina, which has the densest concentration of receptors and a blind spot over the optic nerve. The power of the lens can be adjusted to display the picture at different distances

  • external: cornea and sclera.
  • middle: choroid, ciliary body and iris.
  • inner – retina.

Inside there is an aqueous medium (transparent liquid in the anterior and posterior chambers), the vitreous humor (colorless jelly), and a flexible lens. They are all connected by the pupil.


Automatically adjusts exposure with eye movement. It is the changes in pupil size that allow us to adapt to darkness or brightness. The lens in the eye resembles an element in a camera or glasses. The function of the camera itself is the pupil, and the iris is the diaphragm. Two-thirds of the eye’s power comes from the cornea, and the rest comes from the lens. The image travels through several layers.

A ray of light forms an image on the retina. It converges on the cornea and lens. The rays are traced from above and below, forming an inverted image

Eye movement

The eye has 6 muscles: lateral straight, medial straight, inferior straight, superior straight, inferior oblique and superior oblique. They all create movement, tension and torque. Here are some examples:

  • rapid eye movement – in the stage with the most vivid dreams.
  • the vestibulo-ocular reflex is the opposite of moving the head and keeps the object in the field of view.
  • pursuit – the eyes follow a moving object.

Physics Section

Human eye
  • Human eye
  • Color vision
  • Human eye resolution
  • Nearsightedness, hyperopia and vision correction
Other optical instruments
  • Magnifying glass
  • Camera
  • Compound microscope
  • Telescope
  • X-ray diffraction
  • X-ray imaging and computed tomography
  • Specialized microscopes and contrast
  • Resolution limits and circular apertures
  • Aberrations

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