1565 LUMINESCENCE, FLUORESCENCE, PHOSPHORESCENCE and IRIDESCENCE

1565 LUMINESCENCE, FLUORESCENCE, PHOSPHORESCENCE and IRIDESCENCE –by Gautam Shah

All these words have a suffix or end escence =it expresses the beginning of an action or process, beginning to be, do, show, etc.

These words, here, also relate to heat, energy, warmth, glow and light.

Luminescence commonly mean a radiation emitted by an atom or a molecule following the absorption of energy and transition into an exited state. The word, luminous basically means giving off light. In case of the chemiluminescence, the light emission is due to a chemical reaction.

Fluorescence occurs when a material has ability to absorb light and then emit it at a longer wavelength or lower energy level. The emission takes place immediately, and is only visible as long as the light source has UV component. This is a radiative mechanism, where, electrons transit from low excited state to the normal (no excitement) state.

Phosphorescence the material can store the absorbed energy, and release it later, but also at a longer wavelength or lower energy level. The feeble glow remains, even after a light source is switched off.

Iridescence is an optical phenomenon of surfaces. It occurs when some surfaces change their perceived colour for two main reasons: Change in the angle of view or illumination. It is often caused by multiple reflections from two or more semi-transparent surfaces. Refer to Design Synopsis Blog > 522 IRIDESCENCE.

1465 MOTHER OF PEARL

1465 MOTHER OF PEARL -by Gautam Shah

Mother of Pearl is an iridescent material. Nacre or Mother of pearl is a mixture of defensive secretions or molluscs by oysters and various minerals. It is a coat over the surface of the pearl and oyster. A similar phenomenon is observed on soap bubbles, feathers, butterfly wings, oil floating on water, etc. The vivid colours of a peacock feather are not due to any pigments but the fibers of the feathers.

Iridescence is the change in colour, with the direction of observation and angle of incident light. The colours (or just effects) are produced by the interference or the light diffracting characteristics of the micro-structures. This phenomenon is not by selective reflection or absorption of the light as happens with the pigments. At nano level, the nacre is multi layer composition where each semitransparent aragonite layer reflects part of the light waves and transmits the rest to lower layers. And this gives out iridescent effect of colours.

Mother of pearl is a resilient to fragile materials. These valued for their quality of iridescence, and used in jewellery, decorative embellishments, as an inlay embedded on metal, wood, etc. Pieces of mother of pearl are combined for the orientation, colour tone and grain and joint patterns. Mother pearl surfaces are etched, selectively dyed and coated with shellac lacquer. The iridescence of Mother of Pearl is often contrasted with thin pieces of polished bone for their comparative opacity.