Luminous intensity is a measure of the energy emitted by a light source in a particular direction.

The SI unit of luminous intensity is the candela (cd). The International System of Units (abbreviated SI from the French phrase, Système International dUnités) is the most widely used system of units. ... The candela (symbol: cd, Latin for candle) is one of the seven SI base units. ...

1 cd is that luminous intensity emitted by a monochromatic light source of frequency 540 × 10¹² hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. The hertz (symbol Hz) is the SI unit of frequency. ... The watt (symbol: W) is the SI derived unit for power. ... The steradian (ste from Greek stereos, solid) is the SI derived unit of solid angle, and the 3-dimensional equivalent of the radian. ...

In 1881, Jules Violle proposed the Violle as a unit of luminous intensity, and it was notable as the first unit of light intensity that did not depend on the properties of a particular lamp. It was superseded by the candela in 1946. 1881 was a common year starting on Saturday (see link for calendar). ... Jules Louis Gabriel Violle (November 16, 1841, Langres - September 12, 1923, Fixin) was a French physicist and inventor. ...

It is worth noting that luminous intensity (and other derived quantities) is not an "objective" physical quantity but depends on the physiology of the human eye, especially its sensitivity to light of different frequencies. The eye is most sensitive to light at 540 THz; light at higher or lower frequencies (but with the same physical intensity) represents smaller luminous intensity. The willingness to question previously held truths and search for new answers resulted in a period of major scientific advancements, now known as the Scientific Revolution. ... Physiology (in Greek physis = nature and logos = word) is the study of the mechanical, physical, and biochemical functions of living organisms. ... An eye is an organ that detects light. ... See: Sensitivity (electronics) Sensitivity (human) Sensitivity (tests) For sensitivity in finance, see beta coefficient This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye or, in a technical or scientific setting, electromagnetic radiation of any wavelength. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... A terahertz (THz) is 1012 hertz or a thousand gigahertz, a measure of frequency. ... In physics, intensity is a measure of the time-averaged energy flux. ...

The second (symbol s) is a unit for time, and one of seven SI base units. ... In photometry the Talbot (T) is a nonstandard unit of luminous energy. ... Luminous flux is a measure of the energy emitted by a light source in all directions. ... In physics, specifically photometry (optics), the lumen (symbol: lm) is the SI derived unit of luminous flux. ... The steradian (ste from Greek stereos, solid) is the SI derived unit of solid angle, and the 3-dimensional equivalent of the radian. ... The candela (symbol: cd, Latin for candle) is one of the seven SI base units. ... The word luminance, a synonym for luminosity, means emitting or reflecting light. ... A square metre (US spelling: square meter) is by definition the area enclosed by a square with sides each 1 metre long. ... Illuminance is the total luminous flux incident per unit area. ... The lux (symbol: lx) is the SI derived unit of illuminance or illumination. ... Luminous efficiency is a measure of the proportion of the energy supplied to a lamp that is converted into light energy. ... The watt (symbol: W) is the SI derived unit for power. ...

See also

• Intensity