Incandescent lamps are the original light source where tungsten wire filament heats and glows. It is the most common light source with a low colour temperature and high CRI, casting a warm light. These lamps are inexpensive and are available in a wide variety of sizes and wattages. However, they are not energy efficient because most of the energy they consume is given off as heat.

The glass enclosures are made from a ribbon of hot glass that's first thickened and then blown into moulds to form the bulb shapes. These enclosures are then cooled, cut from the ribbon, and their insides are coated with the diffusing material that gives the finished bulb its soft, white appearance.

The filament is formed by drawing tungsten metal into a very fine wire. This wire, typically only 42 microns (0.0017 inches) in diameter, is first wound into a coil and then this coil itself wound into a coil. The mandrels used in these two coiling processes are trapped in the coils and must be dissolved away with acids after the filament has been annealed.

The finished filament is clamped or welded to the power leads , which have already been embedded in a glass supporting structure. The glass support is inserted into a bulb and the two glass parts are fused together. A tube in the glass support allows the manufacturer to pump the air out of the bulb and then reintroduce various inert gases. When virtually all of the oxygen has been eliminated from the bulb, the tube is cut off and the opening is sealed. Once the base of the bulb has been attatched, the bulb is ready for use.

Halogen is a refinement of the incandescent light bulb, offering crisp, white light; excellent beam control; high lumen maintenance; energy savings; compact size; and longer life, due to the halogen gas, which causes the evaporated tungsten to redeposit on the filament rather then on the glass (like an incandescent bulb).

The use of Krypton gas in incandescent light bulbs results in high efficiency and longer lamp life. Kypton gas possesses a heavier molecular structure and a higher atomic weight than the standard argon gas, thus insuring slower circulation and heat transmission, resulting in slower tungsten filament evaporation. Slower filament evaporation results in reduced blackening of the lamp walls and higher maintenance lumen output. The Krpton gas also eliminates most of the yellow hues and gives off a whiter light.

Halogen Infra-red ( or HIR lamps) retain all of the benefits of standard halogen but are even more efficient. Halogen-IR uses a high-temperature reflective film to coat the inner layer and trap wasted invisible infra-red light within it. This redirected infra-red heats the filament to produce more visable light, resulting in efficiency improvements of over 40% compared with standard halogen lamps. You get the same crisp, white light, beam control, and compactness of the standard halogen lamp.

There are many ways of producing infra-red light. Firstly, any warm surface emits infra-red light. For example, a heat lamp or an electric space heater emits enourmous amounts of it. Thats because the thermal radiation of a warm object lies mostly in the invisible infra-red portion of the electeromagnetic spectrum.

Secondly, many light-emitting electronic devices emit infra-red light. For example, the L.E.Ds in a television remote control unit emit infra-red light. In this case, the infra-red light is emitted by electrons that are moving from one group of quantum levels in a semiconductor, to another group (from conduction levels to valence levels). This emission isn't thermal radiation; it doesnt involve heat.

Lastly, some infra-red light is produced by lasers. In this case, excited atoms or atomic-like systems amplify passing infra-red light to produce enourmous numbers of identical light particals (identical photons). Infra-red industrial lasers are commonly used to machine everything from greetings cards to steel plates.

Neodymium is a type of mineral that is used in the glass of the light bulb to suppress yellow hues and give off a whiter light that is closer to natural daylight.

An incandescent lamp emits much more energy than is included in the visible region. Dichroic coatings and filters are used to seprate heat from light. This process reflects most of the visable light and allows most of the heat to pass through and out of the back of the lamp.

Shatterproof lamps are coated with a plastic coating that, in the event of a breakage, would prevent dangerous exposure of broken glass and mercury. Broken glass is always a hazard and also, a typical fluorescent tube contains enough mercury to pollute over 15,000 litres of water beyond the safe level for drinking.

Until recently, the main means of protection against glass contamination has been to enclose lighting units in sensitive areas within IP65 fittings. However, the main purpose of these fittings is to guard against water, dust, and mould, and they offer no protection in situations where lamps are transported, fitted or removed, and it is in these situations that most breakages actually occur.

p>The glass envelope of an incandescent bulbs can't contain air because tungsten is flammable when hot and would burn up if there was oxygen present around it. One of Thomas Edison's main contributions to the development of such bulbs was learning how to extract all the air from the bulb. But a bulb that contains no gas won't work well because tungsten sublimes at high temperatures (its atoms evaporate directly from solid to gas). If there were no gas in the bulb, every tungsten atom that left the filament would fly unimpeded all the way to the glass wall of the bulb and then stick there permenantly. While there are some incandescent bulbs that operate with a vacuum inside, most common incandescent lamps contain a small amount if argon and nitrogen gases.

Argon and nitrogen are chemically inert, so that the tungsten filament can't burn in the argon and nitrogen, and each argon atom or nitrogen module is massive enough that when a tungsten atom that's trying to leave the filament hits it, that tungsten atom may rebound back onto the filament . The argon and nitrogen gases thus prolong the life of the filament. Unfortunately, these gases also convey heat away from the filament through convection. You can see evidence of this convection as a dark spot of tungsten atoms that accumulate at the top of the bulb. That black snudge consists of tungston atoms that didn't return to the filament and were swept upward as the hot argon and nitrogen gases rose.

However, some premium light bulbs contain krypton gas rather then argon gas. Like argon, Krypton is chemically inert. But a Krypton atom is more massive than an argon atom, making it more effective at bouncing tungsten atoms back towards the filament after they sublime. Krypton gas is also a poorer conductor of heat than argon gas, so that it allows the filament to convert its power more efficiently into visable light. Unfortunately, Krypton is a rare constituent of the atmosphere and is very expensive and thus is only used in premium light bulbs, together with some nitrogen gas.

Incidentally, the filament in many incandescent bulbs is treated with a small amount of a phosphorous-based 'getter' that reacts with any risidual oxygen that may be in the bulb the first time the filament becomes hot. This is how the manufacturer ensures that there will be no oxygen in the bulb for the tungsten filament to react with.

Yes. To begin with, fluorescent lights have a much longer life than incandescent lights (the fluorescent tube lasts many thousands of hours and its fixture lasts tens of thousands of hours). The small amount of energy spent building an incandescent lamp is deceptive because you would have to build alot of those bulbs to equal the value of one fluorescent system.

Secondly, although there is considerable energy consumed in manufacturing the complicated components of a fluorescent lamp, it's unlikely to be more than a few kilowatt-hours, which is the equivalent of the extra energy a 100 watt incandescent lamp uses up in a week or so of typical operation. So, it may take a week or two to recover the energy cost of building the fluorescent light, but after that the energy savings will continue to grow for many years.

Fluorescent tubes produce relatively little heat, so they're relatively fire safe already. However, incandescent lightbulbs become very hot and you have to be carefull with them to avoid fires. Firstly, make sure that the bulb can get rid of its waste heat. That means that you shouldn't wrap the bulb in insulation because it needs to transfer its waste heat to the air. Secondly, keep flammable materials away from the bulb, particularly above the bulb since hot air from the bulb rises upwards.

An incandescent light bulb produces light by heating a small filament of tungsten to about 2500°C. At that temperature, the thermal radiation that the filament emits includes a substantial amount of visible light. But the filament also emits a great deal of infra-red light (heat light) and it also transfers heat via conduction and convection to the glass bulb around it. When you put your hand near the bulb, you feel both the infra-red light and the heat that has worked its way to the surface of the bulb. The bulb feels hot.

In contrast, a fluorescent lamp tries to produce light without heat. It collides electrons with mercury atoms to produce an atomic emission of ultraviolet light. This ultraviolet light is then converted to visible light by the layer of white phosphor powders on the inside of the lamp's glass envelope. In principle, this whole activity can be performed without creating any thermal energy. However, many unavoidable imperfections cause the lamp to convert some of the electric energy it consumes into thermal energy. Nonetheless, the lamp only becomes warm rather than hot.

A heat lamp is much like a normal incandescent lamp, except that the heat lamp's large filament operates at a much lower temperature. Because of this lower temperature, the filament emits realtively little visable light. Instead, it emits mostly invisible infra-red light. While you can't see infra-red light, you can feel it as heat. Looking at a heat lamp is no more dangerous than looking at the glowing coals in a fireplace. Their thermal radiation heats your skin and the surfaces of your eyes, and is likely to make you uncomfortable enough to turn away before it causes real damage. In contrast, ultraviolet light from a sunlamp can injure your skin and eyes without causing any immediate pain; it's only much later that you feel that sunburn on your skin and corneas. That's why a heat lamp is relatively safe while a sunlamp is not.

An incandescent light bulb works by heating a solid filament so hot that the filament's thermal radiation spectrum includes large amounts of visible light. A fluorescent tube uses an electronic discharge in mercury vapour to produce ultraviolet light, which is then transformed into visible light by fluorescent phosphors on the inner surface of the tube. A gas discharge lamp uses an electric discharge in a gas inside that lamp (often high pressure mercury, or sodium vapour, or even neon) to produce visible light directly.

In a common incandescent light bulb, an electric current flows through a double-spiral coil of very thin tungsten wire. As the electric charges in the current flow through this tungsten filament, they collide periodically with the tungsten atoms and transfer energy to those tungsten atoms. The current gives up its energy to the tungsten filament and the filament's temperature rises to around 2500°C. While all objects emit thermal radiation, very hot objects emit some of the thermal radiation as visible light. A 2500°C object emits around 12 % of its heat as visible light and this is the light that you see coming from the bulb. Most of the remaining heat emerges from the bulb as invisible infra-red or 'heat' light. The glass enclosure shields the filament from oxygen because tungsten burns the air./p>

A three-way light bulb has two filaments inside. One filament is smaller than the other, consuming less electricity and emitting less light. At the low light setting, only the smaller filament has current running through it and the bulb emits a dim light. At the medium light setting, only the larger filament has current running through it and the bulb emits a medium light. At the high light setting, both filaments have current running through them and the bulb emits a bright light. To control the two filaments, the bulb as three electrical connections. The two filaments share one of the connections and each has one additional connection of its own. A complicated switch in the lamp determines whether to deliver current to one filament, or the other, or both. In each case, current flows towards the filament through one connection and returns from the filament through the other connection.

A 60 watt light bulb emits about 6 watts of visible light whilst wasting the remaining 54 watts of electric power as other forms of thermal energy. A candle probably also consumes about 60 watts of chemical energy (the paraffin wax), but emits much less than 3 watts of visible light. The light bulb is clearly not very efficient at converting electric power into visible light but the candle is even less efficient. That's because the candle flame operates at a lower temperature (about 1700°C) than the filament of the light bulb (about 2500°C) and the spectrum of light emitted by a hot object depends strongly on its temperature. The cooler flame emits relatively more infrared light and less visible light (particularly blue light) than the hotter filament.

Since only about 80 % of the heat a 60-watt bulb releases is thermal radiation and only about 12 % of that thermal radiation is visible light, the bulb emits about 6 watts of visible light. A halogen bulb is a little more efficient than this and a long-life bulb is a little less efficient than this.