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Luminous energy
 
 
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In photometry
Photometry

Photometry can refer to:*Photometry , the science of measurement of visible light in terms of its perceived brightness to human vision*Photometry , the measurement of the flux or intensity of an astronomical object's electromagnetic radiation...
, luminous energy is the perceived energy
Energy

In physics, energy is a scalar physical quantity that describes the amount of Work_ that can be performed by a force. Energy is an attribute of objects and systems that is subject to a conservation law....
 of light
Light

Light, or visible light, is electromagnetic radiation of a wavelength that is Visible spectrum to the human eye , or up to 380?750 nm. In the broader field of physics, light is sometimes used to refer to electromagnetic radiation of all wavelengths, whether visible or not....
. This is sometimes also called the quantity of light.

Luminous energy is not the same as the radiant energy
Radiant energy

Radiant energy is the energy of electromagnetic waves. The quantity of radiant energy may be calculated by Integral radiant flux with respect to time and, like all forms of energy, its SI unit is the joule....
, the corresponding objective physical quantity
Physical quantity

A physical quantity is a physical property that can be Quantitative. This means it can be measured and/or calculated and expressed in numbers. For example, "weight" is a physical quantity that can be expressed by stating a number of some basic measurement unit such as pound or kilograms, while "beauty" is a property that is difficult to desc...
. This is because the human eye
Eye

Eyes are Organ that detect light, and send signals along the optic nerve to the visual system and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system....
 can only see light in the visible spectrum
Visible spectrum

The visible spectrum is the portion of the electromagnetic spectrum that is visual perception to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light....
 and has different sensitivities to light
Light

Light, or visible light, is electromagnetic radiation of a wavelength that is Visible spectrum to the human eye , or up to 380?750 nm. In the broader field of physics, light is sometimes used to refer to electromagnetic radiation of all wavelengths, whether visible or not....
 of different wavelength
Wavelength

In physics, wavelength is the distance between repeating units of a propagating wave of a given frequency. It is commonly designated by the Greek language letter lambda ....
s within the spectrum. When adapted for bright conditions (photopic vision
Photopic vision

Photopic vision is the visual perception of the eye under well-lit conditions. In humans and many animals, photopic vision allows color vision, mediated by cone cells....
), the eye is most sensitive to light at a wavelength of 555 nm
Metre

The metre or meter is a Unit of measurement of length. It is the SI base unit of length in the metric system and in the International System of Units , used around the world for general and scientific purposes....
.






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Encyclopedia


In photometry
Photometry

Photometry can refer to:*Photometry , the science of measurement of visible light in terms of its perceived brightness to human vision*Photometry , the measurement of the flux or intensity of an astronomical object's electromagnetic radiation...
, luminous energy is the perceived energy
Energy

In physics, energy is a scalar physical quantity that describes the amount of Work_ that can be performed by a force. Energy is an attribute of objects and systems that is subject to a conservation law....
 of light
Light

Light, or visible light, is electromagnetic radiation of a wavelength that is Visible spectrum to the human eye , or up to 380?750 nm. In the broader field of physics, light is sometimes used to refer to electromagnetic radiation of all wavelengths, whether visible or not....
. This is sometimes also called the quantity of light.

Luminous energy is not the same as the radiant energy
Radiant energy

Radiant energy is the energy of electromagnetic waves. The quantity of radiant energy may be calculated by Integral radiant flux with respect to time and, like all forms of energy, its SI unit is the joule....
, the corresponding objective physical quantity
Physical quantity

A physical quantity is a physical property that can be Quantitative. This means it can be measured and/or calculated and expressed in numbers. For example, "weight" is a physical quantity that can be expressed by stating a number of some basic measurement unit such as pound or kilograms, while "beauty" is a property that is difficult to desc...
. This is because the human eye
Eye

Eyes are Organ that detect light, and send signals along the optic nerve to the visual system and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system....
 can only see light in the visible spectrum
Visible spectrum

The visible spectrum is the portion of the electromagnetic spectrum that is visual perception to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light....
 and has different sensitivities to light
Light

Light, or visible light, is electromagnetic radiation of a wavelength that is Visible spectrum to the human eye , or up to 380?750 nm. In the broader field of physics, light is sometimes used to refer to electromagnetic radiation of all wavelengths, whether visible or not....
 of different wavelength
Wavelength

In physics, wavelength is the distance between repeating units of a propagating wave of a given frequency. It is commonly designated by the Greek language letter lambda ....
s within the spectrum. When adapted for bright conditions (photopic vision
Photopic vision

Photopic vision is the visual perception of the eye under well-lit conditions. In humans and many animals, photopic vision allows color vision, mediated by cone cells....
), the eye is most sensitive to light at a wavelength of 555 nm
Metre

The metre or meter is a Unit of measurement of length. It is the SI base unit of length in the metric system and in the International System of Units , used around the world for general and scientific purposes....
. Light with the same power at longer or shorter wavelengths has a lower luminous energy.

Units

The SI
Si

Si, si, or SI may refer to :...
 unit of luminous energy is the lumen
Lumen (unit)

The lumen is the SI unit of luminous flux, a measure of the perceived power of light. Luminous flux differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light....
 second
Second

The second , sometimes abbreviated sec., is the name of a units of measurement of time, and is the International System of Units SI base unit of time....
, which is unofficially known as the Talbot
Talbot (photometry)

In photometry , the talbot is a nonstandard unit of luminous energy, named in honor of the early photographer William Fox Talbot. It is exactly equal to the SI standard unit, the Lumen -second:...
 in honor of William Henry Fox Talbot.

In other systems of units, luminous energy may be expressed in basic units of energy
Energy

In physics, energy is a scalar physical quantity that describes the amount of Work_ that can be performed by a force. Energy is an attribute of objects and systems that is subject to a conservation law....
.

See also

  • Coefficient of utilization
    Coefficient of utilization

    A coefficient of utilization is a measure of the efficiency of a luminaire in transferring luminous energy to the working plane in a particular area....
  • Radiant energy
    Radiant energy

    Radiant energy is the energy of electromagnetic waves. The quantity of radiant energy may be calculated by Integral radiant flux with respect to time and, like all forms of energy, its SI unit is the joule....