Human Eye and Visual Defects

The transparent, bulging front part of the eye, responsible for refracting most of the light entering the eye.

A dark, muscular diaphragm controlling the amount of light entering the eye through the pupil.

The central opening in the iris, allowing light to enter the eye. Its size adjusts based on light intensity.

A transparent, flexible structure behind the pupil, focusing light rays on the retina. Its shape can change to adjust focus for different distances.

Muscles connected to the eye lens, responsible for adjusting lens curvature and focal length to accommodate vision for different distances.

A bundle of nerve fibers connecting the eye to the brain, transmitting visual signals from the retina.

The innermost layer of the eye, containing light-sensitive cells (rods and cones) that convert light into electrical signals for the brain.

The ability of the eye to adjust the focal length of the crystalline lens to focus on objects at varying distances.

The closest point to the eye at which an object can be seen clearly.

The farthest point from the eye at which an object can be seen clearly.

The distance between the near point and the far point of the eye, representing the range of distances the eye can see clearly.

The maximum change in the power of the lens to focus on objects at different distances, allowing the eye to see both near and far objects clearly.

The persistence of an image on the retina for a short time after the object is removed, creating the illusion of continuous movement. This is used in movies and animation.

A defect in vision where the eye cannot see distant objects clearly, but near objects are in focus. It is caused by an elongated eyeball or a too-strong lens.

A defect in vision where the eye cannot see near objects clearly but distant objects are in focus. It's caused by a shortened eyeball or a weak lens.

A vision defect experienced in old age where the eye loses its ability to accommodate and focus on near objects. It is due to the weakening of the ciliary muscles and hardening of the eye lens.

A homogeneous, transparent medium bounded by at least two non-parallel surfaces, used to refract light and split it into different colors.

The phenomenon where white light is separated into its constituent colors (red, orange, yellow, green, blue, indigo, and violet) when it passes through a prism due to the different speeds of each color in the prism.

The band of different colors produced when white light is dispersed through a prism, showing the spectral colors in a specific order.

A natural phenomenon caused by the dispersion of sunlight through water droplets suspended in the atmosphere after rainfall, creating a multi-colored arc in the sky.

The refraction of light that occurs as light passes through the Earth's atmosphere, which consists of different layers of varying densities and refractive indices.

The phenomenon where the direction of light is changed when it interacts with particles such as atoms, molecules, dust particles, or water droplets.

The scattering of light by tiny particles, like dust and water droplets, suspended in air. This effect makes the path of light visible as beams or rays.

The blue color of the sky is caused by the scattering of blue light by tiny particles in the atmosphere. Shorter wavelengths like violet and indigo are scattered more efficiently than longer wavelengths.

The reddish appearance of the sun at sunrise and sunset is due to the scattering of blue light by the thick atmosphere. Red and orange light, with longer wavelengths, aren't scattered as much and reach our eyes.

Clouds appear white because larger water droplets in the atmosphere scatter all colors of light equally, creating a mixture that appears as white.

Red color is used for danger signals because longer wavelengths like red are scattered less by air, smoke, and fog, making them visible even in adverse conditions.

Yellow lights are used in vehicle headlights in foggy weather because their longer wavelength is scattered less than blue light. This allows them to penetrate the fog better and provide better visibility.