| photobleach | To lose colour or make white by the action of light; e.g., the use of a laser to bleach a fluorescent dye covalently linked to a macromolecule. (05 Mar 2000) |
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| photobleaching | <biochemistry> Light induced change in a chromophore, resulting in the loss of its absorption of light of a particular wavelength. A problem in fluorescence microscopy where prolonged illumination leads to progressive fading of the emitted light because less of the exciting wavelength is being absorbed. (18 Nov 1997) |
| photocatalyst | A substance that helps bring about a light-catalyzed reaction; e.g., chlorophyll. Origin: photo-+ G. Katalysis, dissolution (catalysis) (05 Mar 2000) |
| photoceptor | <cell biology> A specialised cell type in a multicellular organism that is sensitive to light. This definition excludes single celled organisms, but includes noneye receptors, such as snake infra red (heat) detectors or photosensitive pineal gland cells. See: retinal rods, retinal cones. (31 Dec 1997) |
| photochemical | <chemistry> Of or pertaining to chemical action of light, or produced by it; as, the photochemical changes of the visual purple of the retina. Origin: Photo- + chemical. Source: Websters Dictionary (01 Mar 1998) |
| photochemistry | <chemistry> The branch of chemistry which relates to the effect of light in producing chemical changes, as in photography. Origin: Photo- + chemistry. Source: Websters Dictionary (01 Mar 1998) |
| photochemotherapy | Therapy using oral or topical photosensitizing agents with subsequent exposure to light. (12 Dec 1998) |
| photochromatic | Of or pertaining to photochromy; produced by photochromy. Source: Websters Dictionary (01 Mar 1998) |
| photochromic | Of or pertaining to photochromy; produced by photochromy. Source: Websters Dictionary (01 Mar 1998) |
| photochromic lens | A light-sensitive spectacle lens that reduces light transmission in sunlight and increases transmission in reduced light. (05 Mar 2000) |
| photochromic spectacles | Spectacles with lenses that darken on exposure to ultraviolet light. (05 Mar 2000) |
| photochromogens | Synonym: group I mycobacteria. Origin: photo-+ G. Chroma, colour, + -gen, producing (05 Mar 2000) |
| photochromy | The art or process of reproducing colours by photography. Origin: Photo- + Gr. Colour. Source: Websters Dictionary (01 Mar 1998) |
| photocoagulation | <technique> A cancer treatment in which a laser is used to destroy blood vessels entering a tumour in order to deprive the tumour of its nutrients. (31 Dec 1997) |
| photocoagulator | The apparatus used in photocoagulation. Laser photocoagulator, a high-energy source of electromagnetic radiation. See: laser. Xenon-arc photocoagulator, a photocoagulator in which a xenon-arc bulb delivers radiation from the visible and near-infrared spectrum. (05 Mar 2000) |