1) The visible surface of the Sun (temperature 5700 K), just below the
→ chromosphere and just above the
→ convective zone.
The solar photosphere is a thin layer of roughly 300 km wide.
Its temperature decreases uniformly with height,
from about 6,600 K (pressure 0.868
→ millibars) at its bottom, to about 4,400 K (pressure 125 mb),
where it merges with the chromosphere. The photosphere has a
"rice-grain" appearance, called
→ granulation, caused by rising (hot) and falling (cool)
material in the → convective cells just below the photosphere.
Other main features of the photosphere are → sunspots,
→ faculae, and → supergranulation.
Of or pertaining to a → photosphere.
The process in green plants, algae, diatoms, and certain forms of bacteria by which carbohydrates are synthesized from carbon dioxide and water using light as an energy source. Most forms of photosynthesis release oxygen as a byproduct.
Fr.: magnitude photovisuelle
Magnitude defined for the combination of a photographic plate and a yellow filter, approximating the spectral sensitivity of the eye.
Fr.: détecteur photovoltaïque
A detector usually constituted by a p-n junction. Upon irradiation, the electron-hole pairs which are created, are immediately separated by the strong electric field across the junction, and a current is generated, which is proportional to the number of incident photons per second.
Fr.: locution, expression
A sequence of two or more words arranged in a grammatical construction and acting as a unit in a → sentence.
From L.L. phrasis "diction," from Gk. phrasis "speech, way of speaking, enunciation," from phrazein "to express, tell," from phrazesthai "to consider."
Pertaining to the physical sciences, especially physics.
Fr.: adsorption physique
Same as → physisorption.
šimi-ye fiziki (#)
Fr.: chimie physique
The branch of chemistry dealing with the relations between the physical properties of substances and their chemical composition and transformations.
Fr.: condition physique
The state of a → physical system regarding its temperature, density, pressure, etc. at a given time.
pâyâ-ye fiziki (#)
Fr.: constante physique
A fundamental → physical quantity that is generally believed to be both universal in nature and constant in time.
Fr.: dimension physique
Any of basic physical quantities, such as mass, length, time, electric charge, and temperature in terms of which all other kinds of quantity can be expressed.
qânun-e fiziki (#)
Fr.: loi physique
A theoretical principle which is deduced from particular observational facts regarding the behavior of matter. Physical laws are expressed by a general statement that a particular → physical phenomenon always occurs if certain → conditions are present.
halâzân-e fiziki, roxgard-e ~
Fr.: libration physique
A real periodic variation in the rotation rate of a celestial object, as distinct from a → geometrical libration. In particular, slight oscillations in the → Moon's rotation caused by the → gravitational attraction of the Earth on the → equatorial bulge of the Moon's near side. The Moon's physical libration is about 0.03° in longitude and about 0.04° in latitude.
Fr.: optique physique
The branch of optics concerned with the wave properties of light, → diffraction, → polarization, and other phenomena for which the ray approximation of → geometric optics is not valid. Also called → wave optics.
Fr.: paramètre physique
padide-ye fiziki (#)
Fr.: phénomène physique
candâ-ye fiziki (#)
Fr.: quantité physique
A physical → property that can be measured and/or calculated.
Fr.: système physique
A set of physical components chosen to study their relations.
A specialist in → physics.