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photoelectric photometer

An instrument for measuring the brightness of a star by means of the electric current produced when its light falls on a light-sensitive surface (the photoelectric effect). The light ...

photometer

photometer   Quick reference

A Dictionary of Physics (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Physics
Length:
103 words

...photometer An instrument used to measure luminous intensity , illumination, and other photometric quantities. The older types rely on visual techniques to compare a source of light with a standard source. More modern photometers use photoelectric cells based on the photoconductive, photoemissive, or photovoltaic effect. The photovoltaic types do not require an external power source and are therefore very convenient to use but are relatively insensitive. The photoemissive type usually incorporates a photomultiplier , especially for use in astronomy and...

photometry

photometry   Quick reference

A Dictionary of Physics (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Physics
Length:
91 words

... In photometry, two types of measurement are used: those that measure luminous quantities rely on the use of the human eye (for example, to compare the illuminance of two surfaces); those called radiant quantities rely on the use of photoelectric devices to measure electromagnetic energy. See also photometer . http://www.kayelaby.npl.co.uk/general_physics/2_5/2_5_3.html Photometric data available at the NPL website...

densitometer

densitometer   Quick reference

A Dictionary of Physics (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Physics
Length:
108 words

...to measure the photographic density of an image on a film or photographic print. Densitometers work by letting the specimen transmit or reflect a beam of light and monitoring the transmitted or reflected intensity. They originally consisted of visual photometers but most instruments are now photoelectric. The simplest transmission densitometer consists of a light source, a photosensitive cell, and a microammeter: the density is measured in terms of the meter readings with and without the sample in place. They have a variety of uses, including detecting the...

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