The Human Eye and the Colourful World

Vocabulary flashcards covering the anatomical structure of the human eye, vision defects, refraction through prisms, and atmospheric optical phenomena.

Retina

A delicate, light-sensitive membrane in the eye where an inverted real image of an object is formed.

Cornea

A thin, transparent membrane forming a bulge on the front surface of the eyeball through which light enters the eye.

Eyeball Diameter

The human eyeball is approximately spherical in shape with a diameter of about $2.3\,cm$.

Iris

A dark muscular diaphragm located behind the cornea that controls the size of the pupil.

Pupil

A structure in the eye that regulates and controls the amount of light entering.

Optic Nerves

The nerves responsible for sending electrical signals generated by light-sensitive cells in the retina to the brain.

Accommodation

The ability of the eye lens to adjust its focal length to focus on both distant and nearby objects.

Least Distance of Distinct Vision

Also called the near point, it is the minimum distance (about $25\,cm$ for a young adult) at which objects can be seen most distinctly without strain.

Far Point

The farthest point up to which the eye can see objects clearly; it is infinity for a normal eye.

Cataract

A condition in old age where the crystalline lens becomes milky and cloudy, causing partial or complete loss of vision.

Myopia

Also known as near-sightedness, a defect where nearby objects are seen clearly but distant objects are blurred; corrected by a concave lens.

Hypermetropia

Also known as far-sightedness, a defect where distant objects are seen clearly but nearby objects are blurred; corrected by a convex lens.

Presbyopia

A vision defect arising from aging due to weakening ciliary muscles and diminishing lens flexibility, making it difficult to see nearby objects clearly.

Angle of the Prism

The angle between the two rectangular lateral surfaces of a triangular glass prism.

Angle of Deviation

The angle formed between the direction of the incident ray and the direction of the emergent ray in a prism.

Dispersion

The splitting of white light into its component seven colours when it passes through a prism.

Spectrum

The band of coloured components (Violet, Indigo, Blue, Green, Yellow, Orange, and Red) produced by the dispersion of a light beam.

Rainbow

A natural spectrum appearing in the sky caused by the dispersion and internal reflection of sunlight by tiny water droplets.

Atmospheric Refraction

The refraction of light by different layers of the earth's atmosphere, which have varying refractive indices.

Tyndall Effect

The phenomenon of scattering of light by colloidal particles, such as smoke or water droplets, making the path of light visible.

Scattering of Light

The process where fine particles deflect shorter wavelengths (like blue) more strongly than longer wavelengths (like red).