light - Maple Help

Units of Light

Description

 • Luminous intensity is a base dimension in the International System of Units.  The SI unit of luminous intensity is the candela,  which is defined as the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency $5.4×{10}^{14}$ hertz and that has a radiant intensity in that direction of 1/683 watt per steradian (16th CGPM, 1979).
 • Luminous flux has the dimension luminous intensity solid angle. The SI unit of luminous flux is the lumen, which is defined as a candela steradian.
 • Luminous luminance has the dimension luminous intensity per length squared. The SI composite unit of luminous luminance is the candela per meter squared.
 • Illuminance has the dimension luminous intensity solid angle per length squared.  The SI unit of illuminance is the lux, which is defined as a candela steradian per square meter.
 • Maple knows the units of light listed in the following table.

 Name Symbols Context Alternate Spellings Prefixes candela cd SI * candelas SI carcel standard * carcels Hefner_unit HK standard * Hefner_units lumen lm SI * lumens SI nit standard * nits lambert Lb standard * lamberts SI footlambert ftLb standard * footlamberts, feetlambert skot standard * skots stilb standard * stilbs apostilb asb standard * apostilbs lux lx SI * lux SI footcandle standard * footcandles, feetcandle nox standard * phot standard * phots candle international candles standard

 An asterisk ( * ) indicates the default context, an at sign (@) indicates an abbreviation, and under the prefixes column, SI indicates that the unit takes all SI prefixes, IEC indicates that the unit takes IEC prefixes, and SI+ and SI- indicate that the unit takes only positive and negative SI prefixes, respectively.  Refer to a unit in the Units package by indexing the name or symbol with the context, for example, candela[SI] or lx[SI]; or, if the context is indicated as the default, by using only the unit name or symbol, for example, candela or lx.
 The units of light are defined as follows.

Luminous Intensity

 A carcel is defined as $10$ candelas.
 A Hefner unit is approximately $0.903$ candela.

Luminous Flux

 The only unit of luminous flux is the lumen.

Luminous Luminance

 A nit is defined as a candela per square meter.
 A stilb is defined as a candela per square centimeter.
 A lambert is defined as $\frac{1}{\mathrm{\pi }}$ candela per square centimeter.
 A footlambert is defined as $\frac{1}{\mathrm{\pi }}$ candela per square foot.
 An apostilb is defined as $0.0001$ lambert.
 A skot is defined as $1.×{10}^{-7}$ lambert.

Illuminance

 A phot is defined as a kilolux.
 A nox is defined as a millilux.
 A footcandle is defined as a lumen per square foot.

Examples

 > $\mathrm{map}\left(\mathrm{convert},\left['\mathrm{cd}','\mathrm{lm}',\frac{'\mathrm{cd}'}{{'m'}^{2}},'\mathrm{lx}'\right],'\mathrm{dimensions}','\mathrm{base}'=\mathrm{true}\right)$
 $\left[{\mathrm{luminous_intensity}}{,}\frac{{\mathrm{luminous_intensity}}{}{{\mathrm{length}}}^{{2}}}{{{\mathrm{length}}{}\left({\mathrm{radius}}\right)}^{{2}}}{,}\frac{{\mathrm{luminous_intensity}}}{{{\mathrm{length}}}^{{2}}}{,}\frac{{\mathrm{luminous_intensity}}}{{{\mathrm{length}}{}\left({\mathrm{radius}}\right)}^{{2}}}\right]$ (1)
 > $\mathrm{map}\left(\mathrm{convert},\left['\mathrm{cd}','\mathrm{lm}',\frac{'\mathrm{cd}'}{{'m'}^{2}},'\mathrm{lx}'\right],'\mathrm{dimensions}','\mathrm{base}'=\mathrm{true},'\mathrm{symbolic}'=\mathrm{true}\right)$
 $\left[{\mathrm{luminous_intensity}}{,}{\mathrm{luminous_intensity}}{,}\frac{{\mathrm{luminous_intensity}}}{{{\mathrm{length}}}^{{2}}}{,}\frac{{\mathrm{luminous_intensity}}}{{{\mathrm{length}}}^{{2}}}\right]$ (2)
 > $\mathrm{convert}\left(23,'\mathrm{units}','\mathrm{stilb}',\frac{'\mathrm{cd}'}{{'m'}^{2}}\right)$
 ${230000}$ (3)
 > $\mathrm{convert}\left(100.0,'\mathrm{units}',\frac{'\mathrm{cd}'}{{'m'}^{2}},'\mathrm{apostilb}'\right)$
 ${314.1592654}$ (4)
 > $\mathrm{convert}\left(1,'\mathrm{units}','\mathrm{footcandle}'{'\mathrm{foot}'}^{2},'\mathrm{lumen}'\right)$
 ${1}$ (5)
 > $\mathrm{convert}\left(1.0,'\mathrm{units}','\mathrm{phot}','\mathrm{lux}'\right)$
 ${10000.0}$ (6)
 > $\mathrm{convert}\left(1.0,'\mathrm{units}','\mathrm{nox}','\mathrm{lux}'\right)$
 ${0.001000000000}$ (7)