SUGGESTIONS FOR CLEAN FIELD

Absorption (EM radiation)

The process by which the energy of a photon is taken up by matter, typically the electrons of an atom. The electromagnetic energy is transformed to another form of energy, e.g. to heat.

Absorption (physical)

A physical or chemical phenomenon or a process in which atoms, molecules, or ions enter some bulk phase - gas, liquid or solid material. This is a different from Adsorption, since the molecules are taken up by the volume, not by surface.

Absorptive Filter

A filter that absorbes some wavelengths of incident radiation whilst transmitting others.

Christiansen Effect

A narrow bandpass or monochromatic optical filter which consists of an optical cell which is stuffed with a crushed substance (e.g. glass) and a (mostly organic) liquid.

Depth of Field

In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image.

Focusing

The gathering of wavefronts of a wave (e.g. radiation) into a spherical or cylindical shape. Focusing of light is used in optics, however focusing can be applied to any radiation or wave.

Magnetic Saturation

Seen in some magnetic materials, saturation is the state reached when an increase in applied external magnetising field cannot increase the magnetisation of the material further, so the total magnetic field levels off. It is a characteristic particularly of ferromagnetic materials, such as iron, nickel, cobalt and their alloys.

Phononic Crystal

A phononic crystal is a material which exhibits stop bands for phonons, preventing phonons of selected ranges of frequencies from being transmitted through the material.

Photoluminescence

A process in which a substance absorbs photons (electromagnetic radiation) and then re-radiates photons. Quantum mechanically, this can be described as an excitation to a higher energy state and then a return to a lower energy state accompanied by the emission of a photon. One of many forms of luminescence (light emission) and is distinguished by photoexcitation (excitation by photons).