LED lamp or LED light bulb is an electric light for use in light
fixtures that produces light using light-emitting diode (LED). LED
lamps have a lifespan and electrical efficiency which are several
times greater than incandescent lamps, and are significantly more
efficient than most fluorescent lamps, with some chips able
to emit more than 300 lumens per watt (as claimed by Cree and some
other LED manufacturers). The
LED lamp market is projected to grow
by more than twelve-fold over the next decade, from $2 billion in the
beginning of 2014 to $25 billion in 2023, a compound annual growth
rate (CAGR) of 25%. As of 2016, LEDs use only about 10% of the
energy an incandescent lamp requires.
Similar to incandescent lamps and unlike most fluorescent lamps (e.g.
tubes and compact fluorescent lamps or CFLs), LEDs come to full
brightness without need for a warm-up time; the life of fluorescent
lighting is also reduced by frequent switching on and off. The
initial cost of LED is usually higher. Degradation of LED dye and
packaging materials reduces light output to some extent over time.
Some LED lamps are made to be a directly compatible drop-in
replacement for incandescent or fluorescent lamps. An LED lamp
packaging may show the lumen output, power consumption in watts, color
temperature in kelvins or description (e.g. "warm white", "cool white"
or "daylight"), operating temperature range, and sometimes the
equivalent wattage of an incandescent lamp of similar luminous output.
Most LEDs do not emit light in all directions, and their directional
characteristics affect the design of lamps, although omnidirectional
lamps which radiate light over a 360° angle are becoming more common.
The light output of single LED is less than that of incandescent and
compact fluorescent lamps; in most applications multiple LEDs are used
to form a lamp, although high-power versions are becoming available.
LEDs, as their name suggests operate as diodes, run on direct current
(DC), whereas mains current is alternating current (AC) and usually at
much higher voltage than the LED can accept. Although low voltage LED
lamps are available LED lamps can contain a circuit for converting the
mains AC into DC at the correct voltage. These circuits contain
rectifiers, capacitors and may have other active electronic
components, which may or may not permit the lamp to be dimmed.
1.1 Examples of early adoption
2 Technology overview
2.1 White light LEDs
2.2 LED drivers
2.3 Thermal management
2.4 Efficiency droop
3.1 Household LED lamp
3.1.1 Lamp sizes and bases
LED tube lamps
Lighting designed for LEDs
4 Comparison to other lighting technologies
4.1 Comparison table
Energy Star qualification
6 See also
8 Further reading
9 External links
Before the introduction of LED lamps, three types of lamps were used
for the bulk of general (white) lighting:
Incandescent lights, which produce light with a glowing filament
heated by electric current. These are very inefficient, having a
luminous efficacy of 10-17 lumens/W, and also have a short lifetime of
1000 hours. They are being phased out of general lighting
Incandescent lamps produce a continuous black body
spectrum of light similar to sunlight, and so produce high Color
rendering index (CRI).
Fluorescent lamps, which produce ultraviolet light by a glow discharge
between two electrodes in a low pressure tube of mercury vapor, which
is converted to visible light by a fluorescent coating on the inside
of the tube. These are more efficient than incandescent lights, having
a luminous efficacy of around 60 lumens/W, and have a longer lifetime
6,000-15,000 hours, and are widely used for residential and office
lighting. However their mercury content makes them a hazard to the
environment, and they have to be disposed of as hazardous waste.
Metal-halide lamps, which produce light by an arc between two
electrodes in an atmosphere of argon, mercury and other metals, and
iodine or bromine. These were the most efficient white electric lights
before LEDs, having a luminous efficacy of 75–100 lumens/W and have
a relatively long bulb lifetime of 6,000-15,000 hours, but because
they require a 5 - 7 minute warmup period before turning on, are not
used for residential lighting, but for commercial and industrial wide
area lighting, and outdoor security lights and streetlights. Like
fluorescents, they also contain hazardous mercury.
Considered as electric energy converters, all these existing lamps are
inefficient, emitting more of their input energy as waste heat than as
visible light. Global electric lighting in 1997 consumed 2016
terawatthours of energy.
Lighting consumes roughly 12% of electrical
energy produced by industrialized countries. The increasing scarcity
of energy resources, and the environmental costs of producing energy,
particularly the discovery of global warming due to carbon emitted by
the burning of fossil fuels, which are the largest source of energy
for electric power generation, created an increased incentive to
develop more energy-efficient electric lights.
The first low-powered LEDs were developed in the early 1960s, and only
produced light in the low, red frequencies of the spectrum. The first
high-brightness blue LED was demonstrated by
Shuji Nakamura of Nichia
Corporation in 1994. The existence of blue LEDs and high-efficiency
LEDs led to the development of the first 'white LED', which employed a
phosphor coating to partially convert the emitted blue light to red
and green frequencies creating a light that appears white.
Isamu Akasaki, Hiroshi Amano and Nakamura were later awarded
Nobel Prize in Physics
Nobel Prize in Physics for the invention of the blue LED.
China further boosted LED research and development in 1995 and
demonstrated its first LED Christmas tree in 1998. The new LED
technology application then became prevalent at the start of the 21st
century by US (Cree) and Japan (Nichia, Panasonic, Toshiba, etc.) and
then starting 2004 by Korea and China (Samsung, Kingsun, Solstice,
In the USA, the Energy Independence and Security Act (EISA) of 2007
authorized the Department of Energy (DOE) to establish the Bright
Lighting Prize competition, known as the "L Prize", the
first government-sponsored technology competition designed to
challenge industry to develop replacements for 60 W incandescent lamps
and PAR 38 halogen lamps. The EISA legislation established basic
requirements and prize amounts for each of the two competition
categories, and authorized up to $20 million in cash prizes. The
competition also included the possibility for winners to obtain
federal purchasing agreements, utility programs, and other incentives.
In May 2008, they announced details of the competition and technical
requirements for each category.
Lighting products meeting the
competition requirements could use just 17% of the energy used by most
incandescent lamps in use today. That same year the DOE also launched
Energy Star program for solid-state lighting products. The EISA
legislation also authorized an additional
L Prize program for
developing a new "21st Century Lamp".
Lighting ceased research on compact fluorescents in 2008 and
began devoting the bulk of its research and development budget to
solid-state lighting. On 24 September 2009,
America became the first to submit lamps in the category to replace
the standard 60 W A-19 "
Edison screw fixture" light bulb, with a
design based on their earlier "AmbientLED" consumer product. On 3
August 2011, DOE awarded the prize in the 60 W replacement category to
LED lamp after 18 months of extensive testing.
Early LED lamps varied greatly in chromaticity from the incandescent
lamps they were replacing. A standard was developed, ANSI
C78.377-2008, that specified the recommended color ranges for
solid-state lighting products using cool to warm white LEDs with
various correlated color temperatures. In June 2008, NIST
announced the first two standards for solid-state lighting in the
United States. These standards detail performance specifications for
LED light sources and prescribe test methods for solid-state lighting
Also in 2008 in the United States and Canada, the
Energy Star program
began to label lamps that meet a set of standards for starting time,
life expectancy, color, and consistency of performance. The intent of
the program is to reduce consumer concerns due to variable quality of
products, by providing transparency and standards for the labeling and
usability of products available in the market. Energy Star
Light Bulbs is a resource for finding and comparing Energy
Star qualified lamps. A similar program in the
United Kingdom (run by
the Energy Saving Trust) was launched to identify lighting products
that meet energy conservation and performance guidelines.
The Illuminating Engineering Society of North America (IESNA) in 2008
published a documentary standard LM-79, which describes the methods
for testing solid-state lighting products for their light output
(lumens), efficacy (lumens per watt) and chromaticity.
In January 2009, it was reported that researchers at University of
Cambridge had developed an
LED lamp that costs £2 (about $3 U.S.), is
12 times as energy efficient as a tungsten lamp, and lasts for 100,000
As of 2016, in the opinion of Noah Horowitz of the Natural Resources
Defense Council, new standards proposed by the United States
Department of Energy would likely mean most light bulbs used in the
future would be LED.
Examples of early adoption
LEDs as Christmas illumination in Viborg, Denmark
In 2008 Sentry Equipment Corporation in Oconomowoc, Wisconsin, US, was
able to light its new factory interior and exterior almost solely with
LEDs. Initial cost was three times that of a traditional mix of
incandescent and fluorescent lamps, but the extra cost was recovered
within two years via electricity savings, and the lamps should not
need replacing for 20 years. In 2009 the Manapakkam, Chennai
office of the Indian IT company, iGate, spent ₹3,700,000 (US$80,000)
to light 57,000 sq ft (5,300 m2) of office space with
LEDs. The firm expected the new lighting to pay for itself within 5
In 2009 the exceptionally large Christmas tree standing in front of
Turku Cathedral in
Finland was hung with 710 LED lamps, each using
2 watts. It has been calculated that these LED lamps paid for
themselves in three and a half years, even though the lights run for
only 48 days per year.
In 2009 a new highway (A29) was inaugurated in Aveiro, Portugal, it
included the first European public LED-based lighting highway.
By 2010 mass installations of LED lighting for commercial and public
uses were becoming common. LED lamps were used for a number of
demonstration projects for outdoor lighting and LED street lights. The
United States Department of Energy
United States Department of Energy made several reports available on
the results of many pilot projects for municipal outdoor lighting,
and many additional streetlight and municipal outdoor lighting
projects soon followed.
LED lamps are often made with arrays of surface mount LED modules (SMD
modules) that replace incandescent or compact fluorescent lamps,
mostly replacing incandescent lamps rated from 5 to 60 watts.
A significant difference from other light sources is that the light is
more directional, i.e., emitted as a narrower beam.
White light LEDs
LED light used in photography
General-purpose lighting requires white light. The first LEDs emitted
light in a very narrow band of wavelengths, of a color characteristic
of the energy band gap of the semiconductor material used to make the
LED. LEDs that emit white light are made using two principal methods:
either mixing light from multiple LEDs of various colors, or using a
phosphor to convert some of the light to other colors.
RGB or trichromatic white LEDs use multiple LED chips emitting red,
green, and blue wavelengths. These three colors combine to produce
white light. The color rendering index (CRI) is poor, typically 25 -
65, due to the narrow range of wavelengths emitted. Higher CRI
values can be obtained using more than three LED colors to cover a
greater range of wavelengths.
The second basic method uses LEDs in conjunction with a phosphor to
produce complementary colors from a single LED. Some of the light from
the LED is absorbed by the molecules of the phosphor, causing them to
fluoresce, emitting light of another color via the Stokes shift. The
most common method is to combine a blue LED with a yellow phosphor,
producing a narrow range of blue wavelengths and a broad band of
"yellow" wavelengths actually covering the spectrum from green to red.
The CRI value can range from less than 70 to over 90, although a wide
range of commercial LEDs of this type have a color rendering index
around 82. Following successive increases in efficacy, which has
reached 150 lm/W on a production basis as of 2017, this type has
surpassed the performance of trichromatic LEDs.
The phosphors used in white light LEDs can give color temperatures in
the range of 2,200 K (matching incandescent lamps) up to 7,000 K or
more. Tunable lighting systems employ banks of colored LEDs that
can be individually controlled, either using separate banks of each
color, or multi-chip LEDs with the colors combined and controlled at
the chip level.
Main article: LED driver
LED chips require controlled direct current (DC) electrical power and
an appropriate circuit as an
LED driver is required to convert the
alternating current from the power supply to the regulated voltage
direct current used by the LEDs.
LED drivers are the essential components of LED lamps or luminaries. A
LED driver can guarantee a long life for an LED system and
provide additional features such as dimming and control. The LED
drivers can be put inside lamp or luminaire, which is called a
built-in type, or be put outside, which is called an independent type.
According to different applications, different types of LED drivers
need to be applied, for example an outdoor driver for street light, an
indoor point driver for a down light, and an indoor linear driver for
a panel light.
Compared to other lighting systems LEDs must be kept cool as high
temperatures can cause premature failure and reduced light output.
Thermal management of high-power LEDs
Thermal management of high-power LEDs is required to keep the junction
temperature close to ambient temperature. LED lamps typically include
heat dissipation elements such as heat sinks and cooling fins and very
high power lamps for industrial uses are frequently equipped with
The term "efficiency droop" refers to the decrease in luminous
efficacy of LEDs as the electric current increases above tens of
milliamps (mA). Instead of increasing current levels, luminance is
usually increased by combining multiple LEDs in one lamp. Solving the
problem of efficiency droop would mean that household LED lamps would
require fewer LEDs, which would significantly reduce costs.
In addition to being less efficient, operating LEDs at higher electric
currents creates higher heat levels which compromise the lifetime of
the LED. Because of this increased heating at higher currents,
high-brightness LEDs have an industry standard of operating at only
350 mA. 350 mA is a good compromise between light output,
efficiency, and longevity.
Early suspicions were that the LED droop was caused by elevated
temperatures. Scientists proved the opposite to be true — that,
although the life of the LED would be shortened, elevated temperatures
actually improved the efficiency of the LED. The mechanism causing
efficiency droop was identified in 2007 as Auger recombination, which
was taken with mixed reaction. In 2013, a study conclusively
identified Auger recombination as the cause of efficiency droop.
LED lamps are used for both general and special-purpose lighting.
Where colored light is needed, LEDs that inherently emit light of a
single color require no energy-absorbing filters.
BAPS Shri Swaminarayan Mandir Atlanta
BAPS Shri Swaminarayan Mandir Atlanta Illumination with color mixing
Computer-led LED lighting allows enhancement of unique qualities of
paintings in the National Museum in Warsaw
White-light LED lamps have longer life expectancy and higher
efficiency (more light for the same electricity) than most other
lighting when used at the proper temperature. LED sources are compact,
which gives flexibility in designing lighting fixtures and good
control over the distribution of light with small reflectors or
lenses. Because of the small size of LEDs, control of the spatial
distribution of illumination is extremely flexible, and the light
output and spatial distribution of an LED array can be controlled with
no efficiency loss.
LEDs using the color-mixing principle can emit a wide range of colors
by changing the proportions of light generated in each primary color.
This allows full color mixing in lamps with LEDs of different
colors. Unlike other lighting technologies, LED emission tends to
be directional (or at least Lambertian), which can be either
advantageous or disadvantageous, depending on requirements. For
applications where non-directional light is required, either a
diffuser is used, or multiple individual LED emitters are used to emit
in different directions.
Household LED lamp
Disassembled LED-light bulb with driver circuit board and Edison screw
Lamp sizes and bases
LED lamps are made with standard lamp connections and shapes, such as
Edison screw base, an MR16 shape with a bi-pin base, or a GU5.3
(bi-pin cap) or GU10 (bayonet fitting) and are made compatible with
the voltage supplied to the sockets. They include driver circuitry to
rectify the AC power and convert the voltage to an appropriate value,
usually a switched-mode power supply.
As of 2010[update] some LED lamps replaced higher wattage bulbs; for
example, one manufacturer claimed a 16-watt
LED lamp was as bright as
a 150 W halogen lamp. A standard general-purpose incandescent
bulb emits light at an efficiency of about 14 to 17 lumens/W depending
on its size and voltage. According to the European Union standard, an
energy-efficient lamp that claims to be the equivalent of a 60 W
tungsten lamp must have a minimum light output of 806 lumens.
A selection of consumer LED bulbs available in 2012 as drop-in
replacements for incandescent bulbs in screw-type sockets
Some models of LED lamps are compatible with dimmers as used for
incandescent lamps. LED lamps often have directional light
characteristics. These lamps are more power-efficient than compact
fluorescent lamps[better source needed] and offer
lifespans of 30,000 or more hours, reduced if operated at a higher
temperature than specified.
Incandescent lamps have a typical life of
1,000 hours, and compact fluorescents about 8,000 hours. The
lamps maintain output light intensity well over their lifetimes.
Energy Star specifications require the lamps to typically drop less
than 10% after 6,000 or more hours of operation, and in the worst case
not more than 15%. LED lamps are available with a variety of color
properties. The purchase price is higher than most other lamps, but
the higher efficiency may make total cost of ownership (purchase price
plus cost of electricity and changing bulbs) lower.
High-power LED "corn cob" light bulb
Several companies offer LED lamps for general lighting purposes. The
technology is improving rapidly and new energy-efficient consumer LED
lamps are available.
As of 2016[update], in the United States, LED lamps are close to being
adopted as the mainstream light source because of the falling
prices and because 40 and 60 watt incandescent lamps are being phased
out. In the U.S. the Energy Independence and Security Act of 2007
effectively bans the manufacturing and importing of most current
incandescent lamps. LED lamps have decreased substantially in pricing
and many varieties are sold with subsidized prices from local
A 17 W tube of LEDs which has the same intensity as a 45 W
LED tube lamps
Main article: LED tube
LED tube lights are designed to physically fit in fixtures intended
for fluorescent tubes. Some LED tubular lamps are intended to be a
drop-in replacement into existing fixtures if appropriate ballast is
used. Others require rewiring of the fixtures to remove the ballast.
LED tube lamp generally uses many individual Surface-Mounted LEDs
which are directional and require proper orientation during
installation as opposed to Fluorescent tube lamps which emit light in
all directions around the tube. Most
LED tube lights available can be
used in place of T8, T10, or T12 tube designations, T8 is D26mm, T10
is D30mm, in lengths of 590 mm (23 in), 1,200 mm
(47 in) and 1,500 mm (59 in).
Lighting designed for LEDs
Newer light fittings designed for LED lamps, or indeed with long-lived
LEDs built-in, have been coming into use as the need for compatibility
with existing fittings diminishes. Such lighting does not require each
bulb to contain circuitry to operate from mains voltage.
Grow light § LEDs(
Light Emitting Diodes)
Experiments revealed surprising performance and production of
vegetables and ornamental plants under LED light sources. A large
number of plant species have been assessed in greenhouse trials to
make sure that the quality of biomass and biochemical ingredients of
such plants is comparable with, or even higher than, those grown in
field conditions. Plant performance of mint, basil, lentil, lettuce,
cabbage, parsley and carrot was measured by assessing both the health
and vigor of the plants and the success of the LEDs in promoting
growth. Also noticed was profuse flowering of select ornamentals
including primula, marigold and stock.
Light emitting diodes (LEDs) offer efficient electric lighting in
desired wavelengths (red + blue) which support greenhouse production
in minimum time and with high quality and quantity. As LEDs are cool,
plants can be placed as close as possible to light sources without
overheating or scorching. This saves a large amount of space for
Flashlight replacement bulb (left), with tungsten equivalent
White LED lamps have achieved market dominance in applications where
high efficiency is important at low power levels. Some of these
applications include flashlights, solar-powered garden or walkway
lights, and bicycle lights. Monochromatic (colored) LED lamps are now
commercially used for traffic signal lamps, where the ability to emit
bright monochromatic light is a desired feature, and in strings of
holiday lights. LED automotive lamps are widely used for their long
life and small size (allowing for multiple bulbs), improving road
safety. LED lamps are also becoming popular in homes, especially for
bathroom and medicine cabinet lighting.
Comparison to other lighting technologies
See luminous efficacy for an efficiency chart comparing various
Incandescent lamps (light bulbs) generate light by passing electric
current through a resistive filament, thereby heating the filament to
a very high temperature so that it glows and emits visible light over
a broad range of wavelengths.
Incandescent sources yield a "warm"
yellow or white color quality depending on the filament operating
Incandescent lamps emit 98% of the energy input as
heat. A 100 W light bulb for 120 V operation emits about 1,700
lumens, about 17 lumens/W; for 230 V bulbs the figures are 1340 lm
and 13.4 lm/W.
Incandescent lamps are relatively inexpensive to
make. The typical lifespan of an AC incandescent lamp is 750 to 1,000
hours. They work well with dimmers. Most older light fixtures
are designed for the size and shape of these traditional bulbs. In the
U.S. the regular sockets are E26 and E11, and E27 and E14 in some
Fluorescent lamps work by passing electricity through mercury vapor,
which in turn emits ultraviolet light. The ultraviolet light is then
absorbed by a phosphor coating inside the lamp, causing it to glow, or
fluoresce. Conventional linear fluorescent lamps have life spans
around 20,000 and 30,000 hours based on 3 hours per cycle according to
lamps NLPIP reviewed in 2006. Induction fluorescent relies on
electromagnetism rather than the cathodes used to start conventional
linear fluorescent. The newer rare earth triphosphor blend linear
fluorescent lamps made by Osram, Philips, Crompton and others have a
life expectancy greater than 40,000 hours, if coupled with a
warm-start electronic ballast. The life expectancy depends on the
number of on/off cycles, and is lower if the light is cycled often.
The ballast-lamp combined system efficacy for then current linear
fluorescent systems in 1998 as tested by NLPIP ranged from 80 to 90
Compact fluorescent lamps' specified lifespan typically ranges from
6,000 hours to 15,000 hours.
Electricity prices vary in different areas of the world, and are
customer dependent. In the US generally, commercial (0.103 USD/kWh)
and industrial (0.068 USD/kWh) electricity prices are lower than
residential (0.123 USD/kWh) due to fewer transmission losses.
High-pressure sodium lamps give around 100 lumens/watt which is very
similar to LED lamps. They have much shorter life than LEDs, and their
color rendering index is low. They are commonly used for outdoor
lighting and in grow lamps.
Cost Comparison for 60 watt incandescent equivalent light bulb (U.S.
residential electricity prices)
LED (EcoSmart clear)
Color temperature kelvin
Lamp lifetime in years @ 6 hours/day
Energy cost over 20 years @ 12.5 cents/kWh
Total cost over 20 years
Total cost per 860 lumens
Comparison based on 6 hours use per day (43,800 hours over 20 yrs)
In keeping with the long life claimed for LED lamps, long warranties
are offered. However, currently there are no standardized testing
procedures set by the Department of Energy in the United States to
prove these assertions by each manufacturer. 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.
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. Low power factors can result in surcharges for
commercial energy users; CFL and LED lamps are available with driver
circuits to provide any desired power factor, or site-wide power
factor correction can be performed. EU standards requires a power
factor better than 0.5 for lamp powers up to 25
Watt and above 0.9 for
higher power lamps.
Energy Star qualification
Energy Star is an international standard for energy efficient consumer
products. Devices carrying the
Energy Star service mark
generally use 20–30% less energy than required by US standards.
Energy Star LED qualifications:
Reduces energy costs — uses at least 75% less energy than
incandescent lighting, saving on operating expenses.
Reduces maintenance costs — lasts 35 to 50 times longer than
incandescent lighting and about 2 to 5 times longer than fluorescent
lighting. No lamp-replacements, no ladders, no ongoing disposal
Reduces cooling costs — LEDs produce very little heat.
Is guaranteed — comes with a minimum three-year
warranty — far beyond the industry standard.
Offers convenient features — available with dimming on some
indoor models and automatic daylight shut-off and motion sensors on
some outdoor models.
Is durable – won't break like a bulb.
To qualify for
Energy Star certification, LED lighting products must
pass a variety of tests to prove that the products will display the
Brightness is equal to or greater than existing lighting technologies
(incandescent or fluorescent) and light is well distributed over the
area lit by the fixture.
Light output remains constant over time, only decreasing towards the
end of the rated lifetime (at least 35,000 hours or 12 annums based on
use of 8 hours per day).
Excellent color quality. The shade of white light appears clear and
consistent over time.
Efficiency is as good as or better than fluorescent lighting.
Light comes on instantly when turned on.
No flicker when dimmed.
No off-state power draw. The fixture does not use power when it is
turned off, with the exception of external controls, whose power
should not exceed 0.5 watts in the off state.
Power factor of at least 0.7 for all lamps of 5W or greater.
Many will not work with existing dimmer switches designed for higher
power incandescent lamps.
Color rendering is not identical to incandescent lamps which emit
close to perfect black-body radiation as that from the sun and for
what eyes have evolved. A measurement unit called CRI is used to
express how the light source's ability to render the eight color
sample chips compare to a reference on a scale from 0 to 100. LEDs
with CRI below 75 are not recommended for use in indoor lighting.
LED lamps may flicker. The effect can be seen on a slow motion video
of such a lamp. The extent of flicker is based on the quality of the
DC power supply built into the lamp structure, usually located in the
lamp base. Longer exposures to flickering light contribute to
headaches and eye strain.
LED efficiency and life span drop at higher temperatures, which limits
the power that can be used in lamps that physically replace existing
filament and compact fluorescent types. Thermal management of
high-power LEDs is a significant factor in design of solid state
lighting equipment. LED lamps are sensitive to excessive heat, like
most solid state electronic components. LED lamps should be checked
for compatibility for use in totally or partially enclosed fixtures
before installation as heat build-up could cause lamp failure and/or
The long life of LEDs, expected to be about 50 times that of the most
common incandescent lamps and significantly longer than fluorescent
types, is advantageous for users but will affect manufacturers as it
reduces the market for replacements in the distant future.
The human circadian rhythm can be affected by light sources.
The effective color temperature of daylight is ~5,700K (bluish
white) while tungsten lamps are ~2,700K (yellow). People who have
circadian rhythm sleep disorders are sometimes treated with light
therapy (exposure to intense blueish white light during the day) and
dark therapy (wearing amber-tinted goggles at night to reduce blueish
Some organizations recommend that people should not use bluish white
lamps at night. The American Medical Association argues against using
bluish white LEDs for municipal street lighting.
Research suggests that since the shift to LED street lighting attracts
48% more flying insects than HPS lamps, which could cause direct
ecological impacts as well as indirect impacts such as attracting more
gypsy moths to port areas.
List of emerging technologies
List of light sources
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Wikimedia Commons has media related to LED lamps.
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