Abstract: This chapter highlights the illumination properties and the concept of photometry. The direct measurement of the strength, or intensity, of a source of light, as the energy emitted by it in unit time in the form of radiation in the visible region of the spectrum, is not easily achieved. The modern unit of luminous intensity is called the new candle or candela. It is defined as the luminous intensity of a source is one-sixth part of the luminous intensity of a source consisting of 1 cm2 of a black body, or full, radiator at the melting point of platinum, viewed normal to the surface. The light energy emitted per unit time from a source is referred to as luminous flux and the unit is the lumen. This is defined as the quantity of luminous flux emitted per unit solid angle by a source of unit intensity, that is, 1 cd, assuming it emits uniformly in all directions. The illumination of a surface is defined as the quantity of luminous flux falling on unit area of that surface. The luminous intensity of a source may not be the same in all directions. The reflection factor of a surface is defined as the fraction of the incident light that is reflected by it.
Publication Year: 1970
Publication Date: 1970-01-01
Language: en
Type: book-chapter
Indexed In: ['crossref']
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Cited By Count: 1
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