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Infrared LEDs are used in remote-control circuits, such as those used with a wide variety of consumer electronics. The first visible-light LEDs were of low intensity and limited to red. Early LEDs were often used as indicator lamps, replacing small incandescent bulbs, and in seven-segment displays.
The wavelength of the light emitted is a function of the band gap of the semiconductor material used; materials such as gallium arsenide, and others, with various trace doping elements, are used to produce different colors of light. Another type of LED uses a quantum dot which can have its properties and wavelength adjusted by its size. Light ...
is the LED's forward voltage drop in volts when lit. and the LED's light frequency (which we perceive as color) increase with the band gap of the LED's materials. Consequently, ranges from around 1.7 to 2.0 volts for red LEDs to around 2.8 to 4.0 volts for violet LEDs.
In frequency (and thus energy), UV rays sit between the violet end of the visible spectrum and the X-ray range. The UV wavelength spectrum ranges from 399 nm to 10 nm and is divided into 3 sections: UVA, UVB, and UVC. UV is the lowest energy range energetic enough to ionize atoms, separating electrons from them, and thus causing chemical reactions.
Round bulbs, often tinted red to reduce visible light, provide infrared radiant heat suitable for warming of people or animals, but the power density available is low. The development of quartz halogen linear lamps allowed much higher power density up to 200 watts/inch of lamp (8 w/mm), useful for industrial heating, drying and processing ...
LEDs produce wavelengths that span from UV-A (350 nm) to near-infrared (NIR) (1100 nm). [14] The wavelength of the LED light can target different tissues. Long wavelength lights such as NIR/dark red(600-1000 nm) can have better tissue penetration and can easily absorb cytochrome c oxidase (CCO) targets by PBMT.
Operation wavelength(s) Pump source Applications and notes Hydrogen fluoride laser: 2.7 to 2.9 μm for hydrogen fluoride (<80% atmospheric transmittance) Chemical reaction in a burning jet of ethylene and nitrogen trifluoride (NF 3) Used in research for laser weaponry, operated in continuous-wave mode, can have power in the megawatt range.
The direct bandgap of AlGaInP encompasses the energy range of visible light (1.7 eV - 3.1 eV). By selecting a specific composition of AlGaInP, the bandgap can be selected to correspond to the energy of a specific wavelength of visible light. For instance, this can be used to obtain LEDs that emit red, orange, or yellow light. [1]