Physics

Bioluminescence

Emission of light by a living organism (e.g., fireflies).

Chemiluminescence

The production of light from chemicals (e.g., glow sticks).

Luminescence

Emission of light from materials that are relatively cool.

Fluorescence

Production of visible light by an object that has absorbed ultraviolet light (e.g., highlighters, fluorescent light bulbs).

Phosphorescence

When a special material phosphors absorb UV light and emit that light over a period of time (e.g., glow in the dark items).

Incandescence

Production of light energy when an object is heated to a high temperature (e.g., regular light bulbs, flame).

Triboluminescence

Emission of light when two crystals are rubbed or crushed together (e.g., two sugar cubes rubbed together).

Electric discharge

An electric current passes through gas, causing it to glow (e.g., lightning, neon lights).

Transparent materials

Materials that let light pass through easily.

Translucent materials

Materials that let some light pass through.

Opaque materials

Materials that do not let any light pass through.

Laws of reflection

The angle of incidence equals the angle of reflection, and incident ray, reflected ray, and normal lie in the same plane.

SALT (image description)

Size, Attitude, Location, Type.

Refraction

Bending of light as it travels from one medium to another of different density.

Index of refraction

The speed of light in a vacuum divided by the speed of light in a medium.

Total internal reflection

Occurs when light travels from a slow to fast medium, bending away from the normal and reflecting back into the medium.

Critical angle

The angle at which the refracted ray equals 90 degrees.