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In photometry, Luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to represent the sensitivity of the human eye. In astronomy, photometry is the measurement of the flux or intensity of an astronomical objects electromagnetic radiation. ...
Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific setting, electromagnetic radiation of any wavelength. ...
Luminous flux or luminous power is the measure of the perceived power of light. ...
This article needs to be cleaned up to conform to a higher standard of quality. ...
Units The SI unit of luminous flux is the lumen (lm). One lumen is defined as the luminous flux of light produced by a light source that emits one candela of luminous intensity over a solid angle of one steradian. In other systems of units, luminous flux may have units of power. The International System of Units (abbreviated SI from the French language name Système International dUnités) is the most widely used system of units. ...
The lumen (symbol: lm) is the SI unit of luminous flux. ...
The candela (symbol: cd, Latin for candle) is one of the seven SI base units. ...
Luminous intensity is a measure of the energy emitted by a light source in a particular direction. ...
The steradian (ste from Greek stereos, solid) is the SI derived unit of solid angle, and the 3-dimensional equivalent of the radian. ...
// Mechanical power In physics, power (symbol: P) is the amount of work W done per unit of time t. ...
Weighting The luminous flux accounts for the sensitivity of the eye by weighting the power at each wavelength with the luminosity function, which represents the eye's response to different wavelengths. The luminous flux is a weighted sum of the power at all wavelengths in the visible band. Light outside the visible band does not contribute. The ratio of the total luminous flux to the radiant flux is called the luminous efficacy. The luminosity function is a standard function established by the Commission Internationale de lÉclairage to account for the variable sensitivity of the human eye to radiation at different wavelengths. ...
A weight function is a mathematical device used when performing a sum, integral, or average in order to give some elements more of a weight than others. ...
Luminous efficacy is a measure of the proportion of the energy supplied to a lamp that is converted into light energy. ...
Contexts Luminous flux is often used as an objective measure of the useful power emitted by a light source, and is typically reported on the packaging for light bulbs, although it is not always prominent. Energy conscious consumers commonly compare the luminous flux of different light bulbs, since it provides an estimate of the apparent amount of light the bulb will produce, and is useful even when comparing different technologies, such as incandescent and compact fluorescent bulbs. For example, a typical 100 watt incandescent light bulb emits about 1700 lumens. Roughly the same amount of light can be produced at a quarter the cost by a 25 watt compact fluorescent light bulb. The article on incandescent light bulbs has more information on the efficiency of different light sources. Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye, or in a more general sense, any electromagnetic radiation in the range from infrared to ultraviolet. ...
Light bulb may be used to refer to many different types of electric lighting, some of which have their own page: Incandescent light bulb, the most common type. ...
An incandescent light bulb and its glowing filament. ...
Compact fluorescent light bulb A compact fluorescent lamp (CFL), also known as a compact fluorescent light bulb, is a type of fluorescent lamp which screws into a regular light bulb socket, or plugs into a small lighting fixture. ...
An incandescent light bulb and its glowing filament. ...
It is wrong or at least imprecise to refer to luminous flux as a measure of "brightness" since, for example, a nearby source of light may appear much brighter than a faraway source with much higher luminous flux. This is because not all of the emitted flux is received by your eye, and you receive less flux from sources that are farther away. In general, brightness has no unambiguous scientific meaning, and should be used only for nonquantitative references to physiological sensations and perceptions of light. Brightness is an attribute of visual perception in which a source appears to emit a given amount of light. ...
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