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The refractive index of silicon is 3.96 (at 590 nm), [2] while air's refractive index is 1.0002926. [3] In general, a flat-surface uncoated LED semiconductor chip emits only light that arrives nearly perpendicular to the semiconductor's surface, in a cone shape referred to as the light cone, cone of light, [4] or the escape cone. [1]
[10] [11] [12] As a photodiode, an LED is sensitive to wavelengths equal to or shorter than the predominant wavelength it emits. For example, a green LED is sensitive to blue light and some green light, but not to yellow or red light. This implementation of LEDs may be added to designs with only minor modifications in circuitry. [10]
A typical domestic LED lamp is stated to have an "average life" of 15,000 hours (15 years at 3 hours/day), and to support 50,000 switch cycles. [ 98 ] Incandescent and halogen lamps naturally have a power factor of 1, but Compact fluorescent and LED lamps use input rectifiers and this causes lower power factors.
The Philips Lighting North America LED bulb won the first competition on August 3, 2011, after successfully completing 18 months of intensive field, lab, and product testing. [94] Efficient lighting is needed for sustainable architecture. As of 2011, some LED bulbs provide up to 150 lm/W and even inexpensive low-end models typically exceed 50 ...
Compared to incandescent bulbs, this is a huge increase in electrical efficiency, and even though LEDs are more expensive to purchase, overall lifetime cost is significantly cheaper than that of incandescent bulbs. [80] The LED chip is encapsulated inside a small, plastic, white mold [81] [82] although sometimes an LED package can incorporate a ...
The "on time" for a 60% duty cycle could be a fraction of a second, a day, or even a week, depending on the length of the period. Duty cycles can be used to describe the percent time of an active signal in an electrical device such as the power switch in a switching power supply or the firing of action potentials by a living system such as a ...
The Germans, however, dissented and decided to use a definition equal to 9/10 of the output of a Hefner lamp. In 1921, the Commission Internationale de l'Eclairage (International Commission for Illumination, commonly referred to as the CIE) redefined the international candle again in terms of a carbon filament incandescent lamp .
Assessment of Advanced Solid State Lighting.National Academies Press. 2013. doi:10.17226/18279. ISBN 978-0-309-27011-3.; Kho, Mu-Jeong, Javed, T., Mark, R., Maier, E., and David, C. (2008) 'Final Report: OLED Solid State Lighting: Kodak European Research' MOTI (Management of Technology and Innovation) Project, Judge Business School of the University of Cambridge and Kodak European Research ...