Subdivisions and characteristics
A characteristic feature of all light sources is the wavelength distribution according to frequency and intensity.
The variety of light sources can be divided according to further criteria: according to the characteristics of measurable radiation, according to the geometry of the beam path or according to individual physical characteristics such as quantum energy . According to the spatial extent of the radiating source, point light sources and diffuse light sources differ, depending on the respective radiation characteristics as all-round or directional radiation.
Physically, a distinction is made between natural, locally limited light sources ( fireflies , aurora , lightning ) and man-made artificial technical light sources ( oil lamp , light source , laser , picture tube , light-emitting diode ).
A self-illuminating light source, also known as an “active light source” or first order light source, generates the emitted light in the light source. These self-luminous elements include the sun, stars, fireflies, fire or lamps.
All other bodies that do not shine themselves are called “passive light sources”, also second or higher order light sources. You can only light by lighting (spotlighting) with other light sources
- emit other colors of light (induced emission), such as luminous colors, or
- reflect the incident light, just as the moon casts sunlight on the earth. These passive sources also include retro reflectors ( cat's eyes ) on means of transport that reflect light.
Thermal emitters deliver continuous radiation, with increasing temperature the radiation maximum shifts from infrared to red, to blue and ultraviolet light (see Planck's law of radiation ). The hotter a heater is, the bluer it appears. The form of energy that is converted into heat and leads to radiation does not matter.
- Electric energy : incandescent lamp , Nernst lamp , the plasma of the carbon arc lamp
- Chemical energy acts primarily during combustion: oil lamps, kerosene lamps, including the high- pressure lamp , gas lantern , candle , torch. In general, with every fire, the flames shine through the glowing, dispersed carbon. A slightly different process is the conversion of heat into (preferably) visible light using a mantle .
- Nuclear physical energy plays the decisive role in the sun as the most original light source for the earth's inhabitants.
In contrast to thermal radiators, molecules and atoms can be brought into an excited state by supplying energy from different sources. If the excited then goes back to the ground state ( recombination ), the difference in energy is released again. For practical use it is of particular importance that this is emitted as radiation with wavelengths in the visible spectral range. The optical component of the resulting radiation is luminescence . With luminescence, two forms are distinguished according to the time between excitation and radiation. Fluorescence only occurs during excitation, whereas phosphorescence also occurs after the external excitation has already ceased. Both are forms of luminescence. Phosphorescence (afterglow after lighting) is used on safety signs, dials or as decoration. In contrast to the continuous spectrum of the thermal emitter, discontinuous spectral lines or bands arise due to the process sequences . Gas discharges in dilute gases show very sharp spectral lines , with gases under pressure (high-pressure metal vapor lamps ) the lines broaden.
The stimulating energy can lead to the light source in different forms of energy. With fireflies or the glow stick , the chemical reaction leads to a reaction and the emission of light. Light-emitting diodes , gas discharge lamps and EL foils are given the function of a light source by means of electric current by means of gas discharge or electroluminescence . Electron bombardment, including beta radiation from a fluorescent luminescent material , stimulates picture tubes and fluorescent displays to light up, including cathodoluminescence and tritium light .
Another category is the conversion of (preferably) UV light through fluorescence into visible light by means of fluorescent materials, these processes of converting shorter (higher-energy) wavelengths to (longer-wave) visible light are fundamental for fluorescent tubes and white light-emitting diodes. Short-wave radiation for the generation of visible light is the X-ray radiation and the gamma radiation for "radioactive" luminous paint in the fluorescent screens of older devices . Synchrotron radiation and Cherenkov radiation , on the other hand, are of no importance as artificial light sources.
Lasers are excited by electrical current, shorter wavelength radiation or chemical energy and are rarely used as a light source. Examples of the practical use of lasers as a light source are infrared target lighting, glare lasers or red laser pointers . The light from green laser pointers is generated by doubling the frequency from an infrared laser beam.
Luminous efficacy of common household lamps
The incandescent lamp, which was slowly dying out in the 2010s, is inferior to the halogen lamp with around 20 lm / W at around 10 lm / W. As the only standard household light source that can still be developed in terms of luminous efficiency , the LED overtook the (compact) fluorescent lamp at around 100 lm / W in the same decade.
Power consumption (
|Luminous efficiency (in lm / W)||
Typical luminous flux (in lumens)
|Basic type||Detail type||minimal||typical||maximum|
|Flame (on wick)||candle||approx. 50||0.1||approx. 5|
|Flame (liquid fuel carburetor) + mantle||High-intensity lamp||up to 1000||5.0||up to 5000|
|Gas flame + mantle||CampinGaz lamp with butane / propane||200|
|Acetylene burner carbide lamp||flat acetylene flame , made of double ceramic nozzle for 14 l / h||200|
|Arc lamp||Charcoal (unfilled) 55 V AC - place lighting||300|
|Arc lamp||Charcoal (filled) 55 V direct current - film projection||1000?|
|Nernst lamp (only: 1899–1913)||Zirconium , yttrium , erbium oxide - room lighting, IR spectroscopy||200|
|Carbon filament light bulb||Carbon thread (historical)||40||<8|
|Incandescent lamp (tungsten)||230 V incandescent lamp||5||5.0||25th|
|230 V incandescent lamp||25th||8th||200|
|230 V incandescent lamp||40||10||10||10.3||400|
|230 V incandescent lamp||60||11.5||12.0||12.5||720|
|230 V incandescent lamp||75||12.4||937.5|
|230 V incandescent lamp||100||13.8||14.5||15.0||1450|
|Halogen light bulb||Halogen 12 V||35||25th||860|
|Halogen 12 V (motor vehicle, real 13.8 V)||55||27.0||27.5||28.0||1512.5|
|Halogen 230 V GU10||50||12||600|
|Halogen 230 V||100||16.7||1670|
|Halogen 230 V||250||16.8||4200|
|Halogen 230 V||500||19.8||9900|
|Halogen 230 V||1000||24.2||24200|
|Gas discharge + fluorescent||Compact fluorescent lamp||11||31.5||49.1||63.6||540.1|
|Compact fluorescent lamp||15th||31.5||56.5||63.3||847.5|
|Compact fluorescent lamp||20th||30th||57.5||67.5||1150|
|Compact fluorescent lamp||23||55||60||60||1380|
|Compact fluorescent lamp||70||75||5250|
|Fluorescent tube , also known as a cold cathode or CCFL||11||50||55||60||605|
|Fluorescent lamp with conventional ballast (KVG, 50 Hz choke)||36||60||75||90||2700|
|Fluorescent lamp including conventional ballast (KVG, 50 Hz choke)||55||40||50||59||2750|
|Fluorescent lamp with electronic ballast (EVG)||36||80||95||110||3420|
|Fluorescent lamp including electronic ballast (EVG)||50||58||68||96||3400|
|Induction lamp (electrodeless fluorescent tube with inductive supply)||80|
|Gas discharge, gas discharge tube||Xenon high pressure gas discharge lamps in video projectors||100 to 300||10||22.5||35||2250 to 6750|
|Xenon gas discharge lamps (high pressure lamps in cinema projectors)||several kilowatts||47|
|Metal halide lamp||35 to 1000||70||94||106||3290 to 94000|
|Mercury vapor lamp high pressure lamp (HID)||50||55||60|
|Glow discharge (neon: orange) without fluorescent material||8th|
|Xenon arc lamp||30th||50||150|
|Mercury xenon arc lamp (vehicle headlights)||35||50-80||52-93||106|
|High pressure mercury vapor lamp (HQL), some with fluorescent material||50||36|
|High pressure mercury vapor lamp, some with fluorescent material||400||60|
|Metal halide lamp (HCI, HQI)||250||93||100||104|
|High pressure sodium lamp||35 to 1000||120||140||150|
|Low pressure sodium vapor lamp||about 80||150||175||200|
|Electroluminescent film (EL film)||EL foil||1.2||5.0||9.0|
|light emitting diode||blue||0.05 to 1||1.0||8.5||16.0|
|red||0.05 to 1||5.0||47.5||90|
|Light emitting diode + fluorescent material||LED chip white (blue + fluorescent)||0.05 to 70||1.0||50.5||231|
|LED chip warm white (blue + fluorescent)||0.05 to 50||1.0||50.5||231|
|LED lamp 230 V white (4000 K; blue + fluorescent)||1 to 20||20th||55||97.14|
|LED lamp 230 V warm white (2700 K; blue + fluorescent)||1 to 20||20th||55||83.92|
|LED lamp 230 V warm white (2700 K; blue + filter)||7 to 12||58.75||75-85||94|
|LED lamp 230 V warm white (2700 K; white + red)||6 to 12||60||68||76|
|technically implemented light output||thermal heater , 6600 K||95|
|theoretical maximum light output||white (5800 K), 400-700 nm||251|
|green, 555 nm - monochrome||683|
In addition to the light yield, the color rendering index is also important for many white spotlights .
- Archived copy ( memento of the original dated February 21, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Nernst Lamp, nernst.de, Walter Nernst Memorial, Ulrich Schmitt, Institute for Physical Chemistry, Georg-August-Universität Göttingen, December 9, 1999, updated June 19, 2013, accessed January 18, 2016.
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- allegedly achieved at 50 W. Nucor GbR, accessed January 6, 2012 .
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- LED spot outdoor construction lights 50W ww. (No longer available online.) Synergy 21, December 8, 2011, formerly in the original ; Retrieved June 27, 2011 . ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- Philips LED 60W 806lm Retrofit with Remote Phosphor. Museum of Electric Lamp Technology, December 24, 2010, accessed January 6, 2012 .
- Philips Master LEDbulb 'Glow' 7W. Museum of Electric Lamp Technology, December 24, 2010, accessed January 6, 2012 .
- MASTER_LED_Designer_Bulb.pdf. (No longer available online.) Philips, December 24, 2010, archived from the original on May 14, 2013 ; Retrieved January 6, 2012 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- L-Prize Bulb partial teardown. (No longer available online.) Doug Leeper, May 6, 2012, archived from the original July 1, 2012 ; Retrieved June 29, 2012 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- New LED record: New technology - new light - lamps. i-Magazin, June 17, 2011, accessed January 6, 2012 .
- “Brilliant-Mix” LED concept ensures warm white, feel-good light. Siemens, May 11, 2011, accessed January 6, 2012 .
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- Tom Murphy: Maximum Efficiency of White Light. July 31, 2011, accessed June 29, 2012 . - Hypothetical black body at 5800 K, which theoretically only emits in the visible range from 400 to 700 nm
- Tom Murphy: Maximum Efficiency of White Light. July 31, 2011, accessed June 29, 2012 . - Hypothetical monochrome radiator at the maximum sensitivity of the eye