Incandescence Limited Historical and technical specifications for fluorescent and LED lamps (Contract 867-5423 history report) Prepared for: Curator of Museum A. Carlisle, Ph.D., P. Eng. Museum of Perth, Australia Victor Blaja, Jan Pachla Electrical Development Department 876 main Street Ottawa, ON G4L 6H1 (666) 616-3845, IncandescenceLimited.com I
Historical and technical specifications for fluorescent and LED lamps Victor Blaja Victor.Blaja@Incandescence.ca Jan Pachla Jan.Pachla@Incendescence.ca April 13, 2016 History Report Electrical Systems Group Department of Electrical Development Incandescence Limited I
Ottawa, April 13, 2016 Letter of Transmittal Incandescence Limited 876 Main Street Ottawa ON G4L 6H1 April 13, 2016 Carlisle Adams Ph. D., P. Eng. Museum of Perth 801 Jackson Street Perth, Australia WA 6000 Historical and technical specifications for LED and Fluorescent lights Dr. Carlisle Adams: Sir, on February 10 th, we came on agreement to contribute to the project of The development of different forms of electrical lighting throughout history by adding LEDs and fluorescent lights. The report will focus on important historical and technical details of the light emitting diodes and the fluorescent lights. Therefore, the Museum of Perth will be able to hold the exhibit about the devices without any historical discrepancy. The project was researched thoroughly with great attention covering LED and fluorescent forms of electrical lighting to provide a clear understanding of the topic. The research was conducted from February 16 th to April 13 th 2016. We recommend the use of original and old relics to construct the exhibit in order to ensure full historical accuracy. Thank you for the opportunity given to work on this project and we hope that you will find the report satisfactory. Sincerely, Victor Blaja Jan Pachla II
Abstract This technical report will present the history, functionality and applications of the fluorescent and LED lamps. The history of the bulbs is covered from the first contributing invention to the most recent light innovations. Their functionality is explained including their components, natural phenomenon and electrical flow. Applications of the light bulbs used today are discussed, as well as comparisons between incandescent LED and fluorescent lamps. Key Words CFL [1]: A compact fluorescent light (CFL) is a fluorescent light bulb that has been compressed into the size of a standard-issue incandescent light bulb. Diode [2]: a semiconductor device with two terminals, typically allowing the flow of current in one direction only. Fluorescence [3]: the visible or invisible radiation emitted by certain substances as a result of incident radiation of a shorter wavelength such as X-rays or ultraviolet light. Incandescent [4]: emitting light as a result of being heated. LED [5]: A light emitting diode (LED) is a semiconductor device that emits visible light when an electric current passes through it Light [6]: the natural agent that stimulates sight and makes things visible. Light bulb [7]: a glass bulb inserted into a lamp or a socket in a ceiling, that provides light by passing an electric current through a filament or a pocket of inert gas Lamp [8]: a device for giving light Semiconductor [9]: a material that can or cannot conduct electricity under certain conditions III
Table of Contents SECTIONS PAGE Title Page...I Letter of Transmittal...II Abstract... III Key Words... III Table of Contents... IV List of Figures... V List of Tables... V Preface... VI Summary... VI CHAPTERS CHAPTER 1 Introduction... 1 CHAPTER 2 The Fluorescent Lamps... 1 CHAPTER 2.1 History of the fluorescent light... 1 CHAPTER 2.2 How fluorescent lamps work... 2 CHAPTER 2.2.1 Components... 2 CHAPTER 2.2.2 Electrical Flow... 3 CHAPTER 2.2.3 Ignition Steps... 3 CHAPTER 2.3 Modern lamps... 4 CHAPTER 2.4 Applications for fluorescent lights... 4 CHAPTER 3 The Light Emitting Diodes... 5 CHAPTER 3.1 History of the light emitting diode... 5 CHAPTER 3.2 How LEDs work... 6 CHAPTER 3.3 Applications for LEDs... 6 CHAPTER 4 Comparison with other light emitting devices... 7 CHAPTER 5 Conclusion... 9 References... 10 IV
List of Figures Figures PAGE Figure 1 - Main components of the fluorescent lamp... 2 Figure 2 - Electrical diagram of the fluorescent lamp... 3 Figure 3 - Ignition of the fluorescent lamp... 3 Figure 4 - Dissection of the fluorescent lamp... 4 Figure 5 - Diagram of the light emitting diode... 6 Figure 6 - Dissection of the light emitting diode... 6 List of Tables Tables PAGE Table 1 - Estimated cost to light a six-foot tree for 12 hours a day for 40 days... 7 Table 2 - Estimated cost of buying and operating lights for 10 holiday seasons... 8 Table 3 - Comparison Chart... 8 V
Preface Since the invention of electrical light, mankind has been relying on it more than any other inventions. It allows humans to work at night and in places where there is no sunlight. A lot of the technology we have today could not have been achieved without inventors such as Heinrich Geissler or Nick Holonyak. The history of the fluorescent light bulb starts with the inventor Heinrich Geissler in 1856 who discovered the first arc lamps. It was only until 1976 when the modern compact fluorescent light was invented, it is one of the most recent designs which was improved in 1984 and that is still used today. The fluorescent lamp uses the movements of electrons to ionize the gas contained inside the lamp causing it to emit light. There are many variations of the fluorescent light but all of them uses the same concept of gas electrification. The light emitting diode made its debut in the 1960 s. It was first an inefficient and costly competitor to the incandescent light bulb and fluorescent light and it was only after the year 2000 that the LED became a viable option compared to other types of lighting solutions. Light emitted by the diode is caused by the movement of electrons in its semiconducting material. The current creates an excess of electrons in the semiconductor which makes the electrons move and that movement generates light. Summary For the fluorescent bulb and LED light, it took many breakthroughs to make the lamps into the compact versions known today. Heinrich Geissler invented the arc tube in 1856. Nikola Tesla created an induction lamp in 1891. In 1895 Daniel McFarlan developed the predecessor to the fluorescent light. Peter Cooper Hewitt made the first commercial mercury vapor lamp in 1901. Edmund Germer advanced fluorescent lamp research by emitting U.V. rays from mercury vapor. In 1926 Edmund Germer produced a malfunctioning fluorescent lamp. In 1934 George Inman along with Richard Thayer, Eugene Lemmers, and Willard A. Roberts developed the first fluorescent lamp. In 1962 Nick Holonyak invented the first LED. Edward E. Hammer designed the modern compact fluorescent lamp in 1976 with the help of Richard Thayer. In the 1980 s the LEDs greatly improved over previous designs. In 1984 John M. Anderson improved the CFL. In the 1990 s the white diode was available and after the year 2000 the LED became the most efficient type of lighting solution. The fluorescent light bulb produces light by the movement of electrons. At the start-up of the fluorescent lamp, a change of alternating voltage is applied ionizing the gas inside the bulb. At the end of each lamp the electrodes electrify the gas. The mercury inside the fluorescent lamp is then affected by the electricity vaporizing and ionizing it. The mercury releases photons at UV frequencies. The photons then pass through the phosphor coating on the lamp creating visible light. VI
The LED releases light through a process called electroluminescence. A current is applied to the semiconductor of the LED causing a build-up of electrons in one of the regions of the semiconductor. Once there is too much electrons they move from one type of material to another. The electron s movement releases energy and the energy released is photons, therefore making light. VII
1. Introduction In the late 1800 s the incandescent light bulbs were the most used bulbs on the market. They were easy to make and were not very expensive to produce. However, they had many limitations so a lot of research was conducted to find solutions to these limitations as well as improving the efficiency of the widely used incandescent light bulb. In the early 1900 s alternatives to the conventional light bulb were invented. One of them was the fluorescent light. These new bulbs were an improvement as they consumed less electricity than the incandescent. Then in the 1960 s the LED was discovered. The newest type of LED lights was revolutionary since they were much more durable and consumed much less electricity than the previous types of lighting devices. Today, fluorescent and LED lights exist and they are a widely used alternative to incandescent lights. The report will cover history, functionality and applications of the different light devices. The history covers the invention of the device to how it has evolved towards this day. The functionality explains the scientific processes used in the lamps to emit light. The applications list the different ways how the light emitting devices could be used for. Extensive research was required to provide an adequate historical report for the museum exhibition. 2. The Fluorescent Lamps 2.1 The history of fluorescent light Throughout modern history there are a number of inventors that have contributed to the development and fabrication of the fluorescent lamp. There are 8 main breakthroughs in the lamp s history, as seen in [10]. In 1856 Bonn Germany, Heinrich Geissler was the first to extensively study the arc tube. His Geissler tube was the foundations for all arc discharge lamps. In 1891 New York city, Nikola Tesla created an induction lamp. His high frequency ballast was a predecessor to modern high frequency regulators used in today s fluorescent lamps. In 1895 New Jersey New York, Daniel McFarlan Moore developed the first predecessor to the fluorescent light called the Moore Tube. The tube was longer and used CO2 and Nitrogen to make a pink and white light. In 1901 New York city, Peter Cooper Hewitt developed the first commercial mercury vapor lamp. An electric arc through mercury vapor is the basis for the modern fluorescent lamp. In 1926 Berlin Germany, Edmund Germer was close to developing the modern fluorescent lamp. His lamp used U.V. rays from mercury vapor. It glowed a greenish color due to his phosphors and had a short life. The hostile conditions in the arc tube corroded the electrodes and destroyed the lamp. The light was not liked by the industry and Germer did not receive any funding to fix the malfunctions. The American General Electric Company bought Germer s patent in 1927. In 1934 Cleveland Ohio, George Inman along with Richard Thayer, Eugene Lemmers, and Willard A. Roberts developed the first fluorescent lamp. Their lamp had real white phosphors, was stable and reliable. The design did not change much for 40 years and 1
is still used today. In 1976 Cleveland Ohio, Edward E. Hammer developed the CFL or compact fluorescent lamp. Working with Richard Thayer at the General Electric company, he designed a more practical lamp that could be used in common households. The lamp had a twisted tube. And in 1984 Schenectady New York, John M. Anderson made improvements in the fluorescent lamp. His variations were: the short arc fluorescent lamp, the fluorescent lamp without ballast, improved electrodes and fluorescent lamp dimming technology. These are the major breakthroughs but the light also borrows inventions from other people like Thomas Edison s screw which is found on most lamps today. The screw to rivets into the fixtures and makes the contact with the current grid. 2.2 How fluorescent lamps work 2.2.1 Components The fluorescent lamp is composed of different parts all of which are important to the functionality of the device, seen in figure 1. The old lamp was also called a preheat light, because during illumination it heated up [11]. This heat was mainly caused by the cathodes emitting excess energy while they were ionizing the molecules around them. The lamp is composed of many components the most important ones being the electrodes, glass tube, inert gas, mercury vapor, electric circuit, phosphor coating, ballast and the starter-switch. The glass tube is sealed shut to prevent the slightly pressurized gas from escaping. The inert gas is commonly Argon, a noble unreactive element. The gas is used to stop the electrodes from eroding and reacting. They would normally chemically react with air if not for the inert gas. There is also a small amount of mercury in liquid form. Because of its important light properties; when electrons pass through mercury they emit photons at UV frequencies. The interior of the lamp is coated with phosphor and when it is bombarded with radiation it produces light. Fluorescence is the property of absorbing light of short wavelength and emitting light of longer wavelength. Phosphor has this property and it is a key phenomenon in the lamp, that is why it is called fluorescent light. Cathodes and anodes are positioned at each end to let electricity pass through the tube. There are two electrodes, one at each end, an anode and a cathode and their roles change when the current direction changes. Each electrode has a filament, a glass base and two electric outlets. The regulator has magnets and electric coil to change the voltage from 110 volts to 216 volts. Also, the regulator protects the lamp from surges and manages the electrical flow throughout the lamp. The starter switch is usually a 1-watt lamp that is used to help the main lamp start. At the start-up the cathodes are cold and Figure 1 Main components of the fluorescent lamp 2
there is no current flow through the lamp. The current then passes through the starter-switch to get electricity to the other end of the lamp. These are the main components of a preheat fluorescent lamp. 2.2.2 Electrical Flow The light emitted by the fluorescent lamp is caused by the movement of electrons inside the tube [12]. Seven steps are required by the fluorescent lamp to produce light, seen in figure 2. Step one starts at the alimentation, the ballast changes the current voltage from 110 volts to 216 volts. The current is always alternative and the voltage increases to sustain the arc. Step two happens at the cathode, when it receives negative current, the cathode starts to ionize gas around it. Step three occurs at the starting lamp. When the gas inside the lamp is not ionized the current cannot flow through it so it bypasses it through the starter. Without it the current would not have any resistance in this path and it could short circuit the system. Step four is at the other end of the tube. When the current switches direction the anode becomes a cathode and it begins to electrify the gas around it. This process of ionization requires quite a bit of energy and it often releases thermal energy which causes the lamp to heat up. In order for the arc to form, a significant amount of gas needs to be electrified. The process requires a lot of time and electricity, since the ignition needs a significant amount of it. This operation strains the electrodes and the lamp system. If the lamp is turned on and off briskly its lifespan could drastically reduce and the tube could even break. Step five, both ends of the tube are ionized. The ballast or regulator gives a surge of electricity to the electrodes to get the arc going. Step six involves the vaporization and ionization of the mercury by the electricity. The mercury is initially at liquid form and when electrons pass through the mercury molecules they release photons at ultraviolet frequencies. Step seven happens when photons pass through the phosphor coating on the lamp. When photons pass through the coating the phosphor converts the frequencies of the photons to visible light frequencies using the phenomenon of fluorescence. After the ignition, the lamp operates at normal power and is stable. Figure 2 Electrical diagram of the fluorescent lamp 2.2.3 Ignition Steps There are a few steps in the ignition of the fluorescent lamp [11]. In the tube there are six start-up steps to ionize the gas and to make the current flow, seen in figure 3. Step one involves the filaments on the electrodes heating up as electricity passes through the circuitry. Step two, the right cathode electrifies gas around it with electrons. Step three, Figure 3 Ignition of the fluorescent lamp 3
the current changes direction and the cathode switches to the left side which ionises the gas around it. Step four, both sides of the tube are heated up and ionized. Step five, the ballast gives a surge of electricity and gets the arc going. Step six the lamp operates as normal. All these processes take only a few seconds and they are repeated every time the lamp starts. 2.3 Modern Lamps Today, fluorescent lights are in the shape of compact fluorescent lights (CFLs). They get their name from a more compact structure of the lamp [11]. The tube has a smaller diameter and it is twisted on itself to occupy less space, seen in figure 4. The lamps today use Edison screws to screw in the light fixtures making them easy to use. They have printed circuit regulators with resistances to start the arc and manage the electric flow through the lamp. The lamps of today are also cold cathode fluorescent lights. They use a better interior coating to make the arc easier to form and less energy is required to operate the lamp. The term cold cathode is used because the lamp s cathodes use less electricity to ionise the gas and thus emit less heat. The compact light is much cooler in operation than the classical lamp. Figure 4 Dissection of the compact fluorescent lamp 2.4 Applications for fluorescent lights Today the fluorescent lights are found everywhere. The components are easy and cheap to fabricate thus the lights are an inexpensive alternative for economic lighting. The lights use less energy to generate light than incandescent. The fluorescent lights are used like neon tubes and street decorations. The coating colour of the fluorescent light can be easily adjusted. They are coated with different colors to provided an aesthetic view. Small ones are used in television liquid crystal display (LCD) screens and in computer monitors. With the new improvements like compact design and a better electrical regulation the lights are widely used in Indoor lighting. With an average wattage of 14 the CFLs save energy and money for consumers [13]. The fluorescent lights do possess a small quantity of mercury which makes them toxic to the environment and they should be handled with care. In short the fluorescent lights are not perfect but they are a practical and cheap way to light up a house. 4
3. The Light Emitting Diodes 3.1 History of the light emitting diode The light emitting diode or in short LED was first discovered in 1962 by Nick Holonyak [10] when he combined gallium, arsenic and phosphorus. The first form of LEDs was red diodes and they had a wavelength of 655 nm. Even if there was not much light emitted from the diode the potential for further development was there. In the 1970 s, yellow and green diodes were made available. The green LED used gallium phosphide (GaP) while the yellow and orange LED used gallium arsenide phosphide (GaAsP) [14]. The early LEDs were used in test equipment, calculators, and digital watches. Even if at that time light emitting diodes were ahead of the incandescent light bulb, the failure rate was greater than that of a conventional light bulb making them quite unreliable. Most of the time, the failure was caused by the actual assembly of the units. There was not yet any mass production of LEDs so therefore some parts had to be made by hand. Sometimes the epoxy covering the light would leak on the diode causing forward or reverse voltage. These leaks caused shortages of the semiconductor resulting in permanent damage. In the 1980 s, gallium aluminum arsenide was discovered to be used in the manufacturing of LEDs. The new material provided a major boost in the performance of light emitting diodes. The efficiency of this new LED technology was over 10 times that of previous designs and it was improving power savings. Gallium aluminum arsenide lights allowed for new applications such as medical equipment, fiber optics and bar code scanners. However, these applications were limited to red 660 nm wavelength and the use of gallium aluminum arsenide degraded the light output. In order to overcome these drawbacks, gallium aluminum arsenide LEDs were replaced by laser diode technology. Indium gallium aluminum arsenide LEDs were developed and they significantly reduced light degradation. Soon after Toshiba developed a new structure using Metal Oxide Chemical Vapor Deposition process that reflected over 90 percent of the light emitted by the diode. This discovery greatly improved the luminescence and efficiency of LEDs making them one of the best light emitting devices on the market. In the early 1990 s the blue diode was discovered. The evolving light spectrum of the LED ensued the eventual discovery of the white diode. The white colour was achieved by coating the blue LED with phosphor giving it the appearance of white light. However true white was later achieved by combining blue, green and red LEDs. White LEDs were a breakthrough because they could be used in all sorts of applications such as flashlights and TVs. In the 2000 s the LEDs gained much more popularity and in 2008 a competition named the L Prize was held with the purpose to encourage the development of solid-state lighting. In late 2009, Philips Lighting North America joined the competition but it was only in 2011 that the company won the first L Prize. The success of the company helped create more competition in the light bulb industry. LEDs had a big push by the Energy Department because they proved to be about seven times more energy efficient as opposed to an incandescent light bulb. In 2008 LEDs had its biggest price drop; LEDs could be purchased for less than $10, a price drop of 85 percent of their original price. Also their lifespan was increased to 25 times that of incandescent light bulbs. 5
3.2 How LEDs work The light emitting diode is more efficient than common light bulbs, but it is because LEDs have a completely different method to emit light. LEDs are a type of solid-state lighting which uses semiconductors to emit monochromatic (single color) light from electric energy [14]. The LED is comprised of a semiconductor die, a lead frame which holds the die in place, an epoxy shell that surrounds the die and electrodes at each end of the semiconductor to direct current in one direction. The light emitted by the LED is made possible by the movement of electrons through a semiconductor usually made out of silicon or germanium. Inside the semiconductor there are electron holes; locations in the material where there are missing electrons. The electron holes can be generated through a process of doping in which other materials are added to the semiconductor to create impurities [16]. The change in materials creates boundaries between the different types of semiconductors inside the same semiconductor. The boundary separating the materials is called a p-n junction and it allows the flow to go only in one direction because of the electrodes [17]. On one side of the semiconductor there is the N-type semiconductor which stands for negative semiconductor because when current is applied it builds up an excess of electrons. The other semiconductor is the P-type because it is positive and it has a lack of electrons also called electron holes. When current flows through the diode the excess electrons from the N-type material jump across the p-n junction to fill the electron holes in the P-type material, seen in figure 6. However, when electrons cross the p-n junction they drop from a high orbital to a lower orbital. This process known as electroluminescence releases energy and that energy is a photon which in turn produces light. The semiconductors are really small, they can be less than a square millimeter in area and the light they emit is pointed in a specific direction. Therefore, LEDs don t need to use reflectors and diffusers which are usually used to reflect the light. 3.3 Applications for LEDs Figure 5 - Diagram of the light emitting diode Figure 6 Dissection of the light emitting diode LEDs are used everywhere in all sorts of different applications because they provide a vast spectrum of colors and they vary in the type of light emitted. LEDs can be used for outdoor or street lighting because they provide a long lifespan as well as direct light and uniform brightness and illumination. LEDs are currently being installed on the Confederation bridge to 6
replace the 315 roadway lights with the goal to reduce power consumption of the bridge by 30% [15]. They are also used for architectural lighting because of their eco friendly nature, directional light and high variety of colors. LEDs can be used for horticultural lighting because of their natural light mimicking the sun. LEDs can be used for portable lights such as flashlights because of their compact form, high beam distance and high intensity. They are used as downlights in houses because they are very power efficient which greatly helps save energy and electricity bill. LEDs can be used as accent lighting since they offer uniform brightness and they can also be used for retail and shop lighting because they enhance the aesthetics of the products [18]. 4 Comparisons with other light emitting devices LEDs are more efficient than common light bulbs, but it when easier to see when LEDs are compared to other types of light bulbs. A light bulb s efficiency is measured in lumens, also by dividing it s light emitted by the power it draws in watts [10]. As an example a 100 percent efficient light bulb would have an efficacy of 683 lm/w while an incandescent bulb of 60-100 watts has an efficacy of 15 lm/w. A compact fluorescent light bulb has an efficacy of about 73 lm/w but a good LED could range from 70 to 120 lm/w. LEDs use less than 75% of the energy used by incandescent bulbs and they can last over 25 times longer than regular bulbs. Compared to incandescent and fluorescent bulbs LEDs can be manufactured in a very small size. Unlike common light bulbs LEDs can emit light in a particular direction making them more efficient because the light is concentrated in an area without the need of reflectors and diffusers to trap the light. Another difference between LEDs and incandescent bulbs is that there is very little heat dissipated by the LEDs. Incandescent bulbs dissipate about 90% of their energy in the form of heat and compact fluorescent lights (CFL) dissipate about 80% of their energy as heat while LEDs barely produce heat. The major lack of heat makes LEDs safer to use than incandescent lights since they can t burn fingers and the risk of combustion is vastly reduced. Since LEDs are made with epoxy lenses, they shatter far less than regular glass bulbs. As a result, LEDs are much safer to handle. The following chart compares the cost of electricity to light a Christmas tree during a certain period of time with 50 C-9 bulbs and 200 mini-lights per tree and electricity at a residential average cost of $ 0.119 kwh in 2012. Table 1: Estimated cost to light a six-foot tree for 12 hours a day for 40 days Incandescent C-9 lights $ 10.00 LED C-9 lights $ 0.27 Incandescent Mini-Lights $ 2.74 LED Mini-lights $ 0.82 7
Table 2: Estimated cost of buying and operating lights for 10 holiday seasons Incandescent C-9 lights $ 122.19 LED C-9 lights $ 17.99 Incandescent Mini-Lights $ 55.62 LED Mini-lights $ 33.29 The next chart [table 3] compares life span, power, temperature of operation, etc. of LEDs, CFL, and incandescent light bulbs, as in [12]. One of the important features of the LED is its long life span. Because of it, they can be used for many more applications than incandescent light bulbs or CFLs since they are much more reliable and require much less maintenance. The power required to light up the LED is much less as well. The amount of 800 lumens is about the light measured on a cloudless day and it is clear that the incandescent bulbs required much more wattage than CFLs or even LEDs. The CFL is the only bulb to contain mercury because it is essential to the way the CFL works but LEDs and incandescent bulbs don t require it. As for temperature and humidity LEDs do not get affected by any changes but incandescent and CFLs do react to variations in temperature and humidity. The LED provides constant light emission while the incandescent slightly gets affected by on/off cycling but not to the same extend as CFLs. The LEDs are much more durable because the semiconductor can be covered using materials such as plastic but incandescent and CFLs are easily breakable because of the glass surrounding them. The LEDs are very efficient because it turns most of the energy into light and very little into heat, however the same is not true for incandescent and CFLs since most of the energy released by the bulb turns into heat, so not all of it is actually light. Heat emitted is measured in British thermal units (BTUs). And finally the failure rate of LEDs is very small compared to incandescent and CFLs. Incandescent and CFLs are easily affected by the elements surrounding them while the LEDs can work in most conditions because they are a solid-state type of lighting device. Table 3: Comparison Chart LED Incandescent CFL Life Span 50,000 hours 1,200 hours 8,000 hours Watts for 800 lumens 6-8 watts 60 watts 13-15 watts Contains Mercury No No Yes Low temperatures Behavior No effect Some alterations Can not work below negative 23C And above 49C Sensitive to humidity No effect Some effect Yes On/off Cycling No Effect Some effect Can reduce lifespan a lot Durability Very Durable, resists blows Not durable, glass breaks Not durable, glass breaks Heat Emitted 3.4 BTU's/hour 85 BTU's/hour 30 BTU's/hour Failure Modes Not Typical Usually overheating filament Yes - may catch on fire, smoke, or omit an odor 8
5. Conclusion In the report we looked at the history of both LED and Fluorescent lights. We examined their components, the functionality of the light emitting devices and we finished with current applications of the different types of light bulbs. The comparison chart shows that the newest type of LED is indeed more durable and more energy efficient than the previous types of lighting devices. Thus they are revolutionary. In conclusion, we provided an accurate depiction of the history and the development of LED and fluorescent lights. For the museum exhibition it is suggested that the manufacturing process of the LEDs and fluorescent lights is presented. And it is recommended to discuss more contributions that inventors made to modern light bulbs. 9
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