Question: What color LED was later created in 1972?
Answer: yellow

Question: What graduate student of Holonyak created the yellow LED?
Answer: M. George Craford

Question: What was the first commercial uses of LEDs?
Answer: replacements for incandescent and neon indicator lamps

Question: How much did the early LEDs cost?
Answer: US$200 per unit

Question: What was one use of early LED light in products?
Answer: calculators

Question: What modern company introduced LEDs in 1968?
Answer: Hewlett Packard (HP)

Question: In what decade were production costs greatly reduced for LEDs to enable successful commercial uses?
Answer: 1970s

Question: What color LED was demonstrated in 1994?
Answer: blue

Question: Who demonstrated the first blue LED?
Answer: Shuji Nakamura

Question: What did Nakamura, Akasaki, and Amano receive for their work?
Answer: 2014 Nobel prize in physics

Question: Who investigated the efficiency of high-brightness LED at Cardiff University in 1995?
Answer: Alberto Barbieri

Question: What substance did Barbieri use in his work with high-brightness LED?
Answer: indium tin oxide

Question: What LED quickly followed the blue LEDs?
Answer: white

Question: What does the YAG phosphor coating produce?
Answer: yellow light

Question: What converts absorbed light energy into an electric current?
Answer: P-N junction

Question: What is the phenomenon where a P-N junction emits light when an electrical current is applied to it?
Answer: electroluminescence

Question: Where are the free electrons located in the production of electroluminescence?
Answer: the conduction band

Question: Whose energy levels are lower than the electrons in the electroluminescence process?
Answer: holes existing in the P-region

Question: Why is some energy in the electroluminescence process emitted as heat and light?
Answer: to recombine the electrons and the holes

Question: In what year was a new type of blue LED produced?
Answer: 2003

Question: Who demonstrated in 2003 the new type of blue LED?
Answer: Cree

Question: How much more efficient as standard incandescents was the white LED commercially available in 2003?
Answer: four times

Question: What is the typical operating current for high-power LEDs?
Answer: 350 mA

Question: What is a symptom of LED failure?
Answer: loss of efficiency

Question: What is rare in LED lighting?
Answer: Sudden failures

Question: What was notable in early red LEDs?
Answer: their short service life

Question: What could cause early light-output degradation in LEDs?
Answer: higher junction temperatures

Question: What is a classification used in LED lighting to describe how much usefulness it will receive?
Answer: L70 or L50

Question: LED efficacy is inversely proportional to what?
Answer: operating temperature

Question: Where is LED lighting very well suited?
Answer: supermarket freezer

Question: LEDs produce less waste heat than what other device?
Answer: incandescent lamps

Question: What is LED lighting more susceptible to than incandescent light?
Answer: frost

Question: What students developed the first blue-violet LED?
Answer: Herb Maruska and Wally Rhines

Question: The first blue-violet LED was developed at what University?
Answer: Stanford

Question: When was the first blue-violet LED developed?
Answer: 1972

Question: What substance helped demonstrate the first blue electroluminescence?
Answer: zinc-doped gallium nitride

Question: In what decade were breakthroughs made that brought in the modern era of GaN-based optoelectronic devices?
Answer: 1980s

Question: Who first patented a method to produce high-brightness blue LEDs?
Answer: Shuji Nakamura

Question: Who first invented a method to produce high-brightness blue LEDs?
Answer: Dr. Moustakas

Question: What technology was made possible by high-power blue light sources?
Answer: BlueRay

Question: What is one modern gadget that benefits from high-power blue LED lighting?
Answer: tablets

Question: What Nobel Prize did Nakamura, Amano, and Akasaki receive in 2014?
Answer: Physics

Question: What award did Nakamura receive in 2006 for his invention?
Answer: Millennium Technology Prize

Question: How many companies did a judge say infringed on Dr. Moustakas's prior blue light patent in 2015?
Answer: three

Question: What was the fine given to the three companies?
Answer: not less than 13 million USD

Question: What are cladding layers?
Answer: active region consisting of one or more InGaN quantum wells sandwiched between thicker layers of GaN

Question: How can light emission be varied from violet to amber?
Answer: By varying the relative In/Ga fraction in the InGaN quantum wells

Question: What does AlGaN stand for?
Answer: Aluminium gallium nitride

Question: What LEDs are more efficient when produced from the InGaN/GaN systems than without?
Answer: Green

Question: What substance does nitrides contain?
Answer: aluminium

Question: What sort of LEDs are becoming more available on the market?
Answer: Ultraviolet

Question: What is the range of wavelengths for cheap UV LEDs?
Answer: 375–395 nm

Question: Shorter wavelength diodes provide wavelengths as low as what?
Answer: 240 nm

Question: What UV wavelengths are found in sterilization devices?
Answer: 250–270 nm

Question: What colors are used to form white light?
Answer: red, green, and blue

Question: What is the method called that mixes red, green, and blue colors to form white light?
Answer: multi-color white LEDs

Question: What does the multi-color white LED method need to produce the end result?
Answer: electronic circuits

Question: What is another name to reference the multi-color white LED method?
Answer: RGB LEDs

Question: What is a factor that may be different in the various types of multi-color white LEDs?
Answer: luminous efficacy

Question: Higher efficiency in multi-color white LEDs may mean what?
Answer: lower color rendering

Question: What is one type of multi-color white LED?
Answer: tetrachromatic

Question: What type has the best luminous efficacy?
Answer: dichromatic white LEDs

Question: What luminous efficacy does trichromatic white LEDs have?
Answer: >70 lm/W

Question: Multi-color LEDs offer what else besides the formation of white light?
Answer: to form light of different colors

Question: What problem must be solved before multi-color LEDs can play a role in the market?
Answer: power decays exponentially with rising temperature

Question: What problem results when rising temperatures decays power?
Answer: substantial change in color stability

Question: What method involves coating LEDs of one color with phosphors of different colors?
Answer: phosphor-converted white LEDs (pcLEDs)

Question: In pcLEDs method, a fraction of what light is used?
Answer: blue

Question: What shift does blue light undergo in the pcLEDs method?
Answer: Stokes

Question: The different colors of phosphors that can be used is based on what?
Answer: the color of the original LED

Question: What broadens the emitted spectrum in a pcLEDs method?
Answer: If several phosphor layers of distinct colors are applied

Question: What do phosphor-based LEDs luminous efficacies depend on?
Answer: the spectral distribution of the resultant light output

Question: What is the most popular method for making high-intensity white LEDs?
Answer: phosphor method

Question: Why is efficiency sometimes lost in phosphor-based LEDs?
Answer: heat loss from the Stokes shift

Question: What are some of the luminous efficacies of yellow phosphor based white LED compared to blue?
Answer: 3 to 5 times the luminous efficacy

Question: What type of emitter is used in phosphor-based white LED methods?
Answer: monochrome

Question: What can improve the efficiency of LED-based white light?
Answer: more efficient phosphors

Question: What is the most efficient yellow phosphor?
Answer: YAG phosphor

Question: What is the percentage of stoke shift loss in YAG phosphor?
Answer: less than 10%