PIEZOELECTRIC EFFECT 



3. Often erroneously used for biolumines- 

 cence, which is a chemiluminescence. 



phosphorescent wheel — A plienomenon which 

 when fully developed gives the appearance of a 

 wheel of light revolving around a point source 

 on or just beneath the sea surface. Various 

 stages of development and sizes of wheels have 

 been reported. The vast majority of wheels 

 have been observed in oceans bordering southern 

 Asia and in the Indonesian Arcliipelago. 



photic zone — See euphotic zone. {See figure for 

 classification of marine environments.) 



photoautotrophic nutrition — See holophytic 

 nutrition. 



photoconductive cell — A photocell whose elec- 

 trical conductance changes under irradiation. 

 A voltage supply is required in the cell circuit. 

 (8) 



photoelectric effect — A process by which a pho- 

 ton ejects an electron from an atom. All the 

 energy of the photon is absorbed in ejecting the 

 electron and in imparting kinetic energy to it. 

 (70) 



photoemissive cell — A photocell whose working 

 depends upon the photoemissive effect, that is, 

 the capacity of certain surfaces to release elec- 

 trons under the influence of radiant energy. 

 (8) 



photogenic granules — Chemical substances in the 

 form of granules associated with biolumines- 

 cence. The granules may be within luminous 

 organs (photophores) or scattered within the 

 surface layer of the body, or they may be se- 

 creted into the environment where they create 

 extracellular bioluminescence. 



photomultiplier cell — A tube (valve) in which 

 secondary emission multiplication is used to in- 

 crease the output for a given incident radiant 

 energy. (8) 



photomultiplier tube — An electronic device which 

 converts photon interactions at the photocathode 

 into measurable electrical pulses. 



It is utilized for measuring light intensity in 

 the ocean and in gamma ray detection 

 instrumentation. 



photon — A quantity of electromagnetic energy 

 whose value in ergs is the product of its fre- 

 quency {v) in cycles per second and Planck's 

 constant (h). The equation is: E=hv. (70) 



photophore — A luminous organ, resembling an 

 eye, within which light is produced either by 

 chemical reactions controlled by the organism or 

 by luminous bacteria living within the cells. 

 Photophores occur most commonly in marine 

 organisms inhibiting the middepths. 



photosynthesis — The manufacture of carbohy- 

 drate food from carbon dioxide and water in the 

 presence of chlorophyll, by utilizing light ener- 

 gy and releasing oxygen. 



phototrophic nutrition — ^^S'ee holophytic nutri- 

 tion. 



ALUMINUM FOIL 



PHOTOCATHODE 



PHOTOMULTIPLIER 

 TUBE 



DIAGRAMMATIC REPRESENTATION 

 OF A SCINTILLATION COUNTER 



photovoltaic cell — A photocell which sets up a po- 

 tential difference between its terminals when ex- 

 posed to radiant energy. It is a self contained 

 current and voltage generator. 



Note: Tlie term "barrier-layer" cell is depre- 

 cated. (8) 



phyllosoma larva — A modified schizopod stage 

 of the spiny lobsters; it is planktonic, paper 

 thin, and transparent. 



phyllum — See classification of organisms. 



physical oceanography — The study of the physi- 

 cal aspects of the ocean, such as its density, tem- 

 perature, ability to transmit light and sound, 

 and sea ice; the movements of the sea, such as 

 tides, currents, and waves ; and the variability of 

 these factors both geographically and temporal- 

 ly in relationship to the adjoining domains, 

 namely, the atmosphere and the ocean bottom. 



physical properties — The physical characteristics 

 of sea water ; for example, temperature, salinity, 

 density, velocity, sound, electrical conductivity, 

 and transparency. (35) 



phytoplankton — The plant forms of plankton. 

 They are the basic synthesizers of organic mat- 

 ter (by photosynthesis) in the pelagic division. 

 The most abundant of the phytoplankton are 

 the diatoms. 



phytoplankton bottle — 1. A container for taking 

 up a sample of water at a desired depth in order 

 to obtain a quantitative sample of phytoplank- 

 ton by filtration in the laboratory. 



2. See vacuum filtration, Millepore* filter. 



phytoplankton equivalent — See plankton equiv- 

 alent. 



picocurie — One micro-microcurie or 10"^- curie. 



piezoelectric effect — The phenomenon, exhibited 

 by certain crystals, in which mechanical com- 

 pression produces a potential difference between 

 opposite crystal faces, or, an applied electric 



207-109 0—66- 



123 



