Optics and Light Vocabulary

Vocabulary flashcards covering key concepts, definitions, and terminology of light, reflection, and optics.

Angle of Reflection

The angle measured between the reflected ray and the normal line.

Bioluminescence

The production and emission of light by a living organism through a chemical reaction (e.g., fireflies, deep-sea fish).

Centre of Curvature ($C$)

The center of the imaginary sphere whose surface forms a curved mirror.

Chemoluminescence

The generation of light directly from a chemical reaction with little or no heat produced and without involving a living organism (e.g., glow sticks).

Diffused Reflection

The scattering of light rays in many different directions when light reflects off a rough or irregular surface.

Electric Discharge

The production of light by passing an electric current through a gas (e.g., neon signs, lightning).

Electromagnetic Wave

A wave consisting of oscillating electric and magnetic fields that travels through a vacuum at the speed of light.

Fluorescence

The immediate emission of visible light caused by the absorption of ultraviolet (UV) light, which stops as soon as the UV source is removed.

Focal Point ($F$)

The point on the principal axis where light rays parallel to the principal axis converge (or appear to diverge) after reflecting off a mirror.

Fusion Reaction

A nuclear reaction where light atomic nuclei combine to form a heavier nucleus, releasing massive amounts of light and thermal energy (e.g., powers the Sun).

Incandescence

The production of light as a direct result of heating an object to a high temperature (e.g., incandescent light bulb filament).

Incident Ray

A ray of light travelling toward a surface before hitting it.

Inverted Image

An image that is oriented upside down relative to the original object.

LED (Light-Emitting Diode)

An electronic semiconductor device that emits light efficiently when electric current flows through it.

Luminescence

The emission of light by a material that does not require high heat ("cold light").

Luminous

Describing an object that generates and emits its own light (e.g., the Sun, a lit candle).

Medium

Any physical substance or material through which light energy travels (e.g., air, water, glass).

Non-Luminous

Describing an object that does not produce its own light and can only be seen by reflecting light from another source (e.g., the Moon, a book).

Normal

An imaginary line drawn perpendicular ($90^\circ$) to a reflecting surface at the point of impact.

Phosphorescence

The absorption of UV light followed by the delayed, persistent emission of visible light over a long period after the light source is removed (e.g., glow-in-the-dark stickers).

Plane Mirror

A flat reflecting surface that forms virtual, upright, laterally inverted images of identical size to the object.

Principal Axis

The imaginary straight line passing through both the Centre of Curvature and the Vertex of a curved mirror.

Ray

A straight line with an arrow showing the path and direction in which light travels.

Real Image

An image formed by the actual intersection of light rays that can be projected onto a physical screen (always inverted relative to the object).

Reflected Ray

A ray of light that bounces off a surface away from the point of impact.

Regular Reflection

Reflection off a smooth, shiny surface where parallel incident rays reflect parallel to each other, forming a clear image (also called specular reflection).

SALT

An acronym used to describe image characteristics: Size (larger, smaller, same), Attitude (upright, inverted), Location (behind, in front, distance), and Type (real, virtual).

Vertex ($V$)

The geometric center point where the principal axis intersects the surface of a curved mirror.

Virtual Image

An image formed behind a mirror where light rays only appear to originate; it cannot be captured on a screen (always upright relative to the object).

Visible Light

The narrow band of the electromagnetic spectrum that human eyes can detect.