The Human Eye and the Colorful World Flashcards

Vocabulary flashcards reviewing human eye anatomy, vision defects, power of accommodation, prism optical phenomena, atmospheric refraction, and scattering of light.

Cornea

The front bulged-out transparent portion of the eyeball through which light enters the eye.

Aqueous Humour

A watery liquid filled in the space between the cornea and eye lens that maintains pressure and provides nutrients to the cornea and lens.

Vitreous Humour

A jelly-like material filled in the space between the eye lens and the retina that helps hold the eye's typical spherical shape.

Iris

A dark muscular diaphragm located between the cornea and the lens that controls the size of the pupil and determines eye color.

Pupil

The small opening in the iris through which light enters the eye; it contracts in bright light and expands in dim light.

Retina

The innermost layer at the backside of the eyeball containing about $125\text{ million}$ light-sensitive receptor cells (rods and cones).

Optic Nerve

A collection of millions of nerve tissues connecting the light-sensitive cells of the retina to the brain to transmit electrical signals.

Eye Lens

A transparent structure composed of fibrous, jelly-like material that provides finer focal adjustments to focus objects onto the retina.

Ciliary Muscles

Muscles attached to the eye lens that hold it in position and alter its curvature to change focal length.

Power of Accommodation

The maximum variation of the eye's power to focus distinctly on near and distant objects by altering the curvature of the eye lens.

Near Point

The minimum distance at which an object can be seen most distinctly without eye strain, which is $25\,\text{cm}$ for a normal human eye.

Far Point

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

Horizontal Field of View

The angular extent of vision observable by the eyes, measuring about $150^\circ$ with one eye open and $180^\circ$ with both eyes open.

Myopia

A defect of vision (nearsightedness) where a person sees nearby objects clearly but cannot see distant objects distinctly because the image forms in front of the retina.

Hypermetropia

A defect of vision (farsightedness) where a person sees distant objects clearly but cannot see nearby objects distinctly because the image forms behind the retina.

Presbyopia

An age-related loss of accommodation power where an aged person fails to see nearby objects clearly due to weakening ciliary muscles and reduced lens flexibility.

Cataract

A condition in old age where the crystalline eye lens becomes milky and cloudy due to membrane growth, causing partial or complete vision loss.

Prism

A transparent refracting medium bounded by at least two lateral surfaces inclined to each other at a specific angle.

Dispersion of White Light

The phenomenon of splitting white light into its constituent colors when passing through a refracting medium like a glass prism.

Spectrum

The band of seven constituent colors (VIBGYOR: Violet, Indigo, Blue, Green, Yellow, Orange, Red) obtained when white light undergoes dispersion.

Recombination of White Light

The process of recombining seven spectrum colors back into white light by passing them through a second identical prism placed in an inverted position.

Rainbow

A natural spectrum in the sky caused by dispersion, refraction, and internal reflection of sunlight by tiny spherical raindrops.

Atmospheric Refraction

The refraction of light caused by passing through Earth's atmospheric layers of varying optical densities.

Apparent Position of Stars

The higher perceived location of a star near the horizon caused by continuous atmospheric refraction bending starlight toward the normal.

Advance Sunrise and Delayed Sunset

The phenomenon where the sun appears visible $2\text{ minutes}$ before actual sunrise and $2\text{ minutes}$ after actual sunset due to atmospheric refraction.

Scattering of Light

The phenomenon where light is reflected or redirected in all directions upon hitting microscopic particles in a medium.

Tyndall Effect

The scattering of light by colloidal or microscopic particles in a heterogeneous mixture, making the pathway of the light beam visible.

Angle of Deviation

The angle formed between the extended direction of the incident ray and the emergent ray after passing through a prism.