WHAT IS LIGHT ?WHAT IS LIGHT ?

When we really think about it, light is one When we really think about it, light is one of the great mysteries. We think in terms of the great mysteries. We think in terms of “seeing” light but don’t really “see” it of “seeing” light but don’t really “see” it at all. Look directly at the sun, an at all. Look directly at the sun, an illuminated bulb, a flame, a flashlight illuminated bulb, a flame, a flashlight beam – do you really see anything? beam – do you really see anything?

In a clean, dark place consider a light In a clean, dark place consider a light beam from a source, such as a powerful beam from a source, such as a powerful flashlight. In the darkness we don’t see flashlight. In the darkness we don’t see anything. Turn on the light beam and anything. Turn on the light beam and what do we see? An object that is what do we see? An object that is illuminated by the beam. illuminated by the beam.

Simply said, we see an object, only Simply said, we see an object, only with the aid of the presence of an energy with the aid of the presence of an energy we call light. That is truly amazing, and it we call light. That is truly amazing, and it even comes in colors. even comes in colors.

THE VISUAL SENSETHE VISUAL SENSE

VISION – VISION – one of the five sensesone of the five senses – – impossible impossible without light . without light .

1) 1) So what is light? It is electromagnetic So what is light? It is electromagnetic energy at a frequency that energy at a frequency that enables enables the visual the visual sense.sense.

2) Visual sensations are recorded in the 2) Visual sensations are recorded in the mind. Creativity in the visual arts comes from mind. Creativity in the visual arts comes from your ability to imagine, with the help of the your ability to imagine, with the help of the things you have seen – which are the things you have seen – which are the recorded visual sensations. recorded visual sensations.

3) Light energy through visual sensation 3) Light energy through visual sensation contributes to one’s well being in that it has contributes to one’s well being in that it has positive affects our physiological state. It positive affects our physiological state. It contributes to balance.contributes to balance.

LIGHT ENERGYLIGHT ENERGY

1) Electromagnetic energy originally 1) Electromagnetic energy originally comes from the sun, although it can be comes from the sun, although it can be created artificially. The energy is created artificially. The energy is measurable, in that it has frequency and measurable, in that it has frequency and wave length – over a very wide spectrum. wave length – over a very wide spectrum. Light energy is a small portion within the Light energy is a small portion within the electromagnetic spectrum that we call electromagnetic spectrum that we call visible light – actually a misnomer, visible light – actually a misnomer, because because we don’t actually SEE the lightwe don’t actually SEE the light – – we see objects as a result of the presence we see objects as a result of the presence of that energy.of that energy.

2) Electromagnetic energy affects not only 2) Electromagnetic energy affects not only our ability to see, but other senses such as our ability to see, but other senses such as hearing by sound, or touch as in hearing by sound, or touch as in temperature – all of which contribute to temperature – all of which contribute to our physical and mental well being. our physical and mental well being.

10410101010 8121620

RADIOTVRADAR

INFRAREDUV

XRAYGAMMACOSMIC RAYS RAYS

AUDIB LESOUND

Frequency in cycles per second ( hertz )

thevisible

spectrum

780380 700600500400

RED

ORANGE

GREEN

YELLOWVIOLET

INDIGOBLUE

Wavelength in nanometers ( 10 meter )-9

THE ELECTROMAGNETIC SPECTRUM

400 500 600 700380 780-9

THE ELECTROMAGNETIC SPECTRUM

YELLOW

GREEN

spectrumvisible

the

Frequency in cycles per second ( hertz )

COSMIC

INDIGOVIOLET

BLUE

RAYSGAMMA

RAYS

1020

UVXRAY

1016

ORANGE

RED

INFRARED

1012

RADAR

10TV

8

SOUNDAUDIB LERADIO

104

Wave length

you have the frequency of redwaves into one second andcram 15,quintillion of theseFREQUENCY

secondone

x

700 times that numberis the wavelength ofred

nanometersyou have nearly four10 million parts anddivide an inch intoWAVELENGTH

y

LIGHT, COLOR, AND CONTRASTLIGHT, COLOR, AND CONTRAST

Full Spectrum Light – the “visual range of light” Full Spectrum Light – the “visual range of light” shown on the electromagnetic scale which shown on the electromagnetic scale which includes red, orange, yellow, green, blue, indigo, includes red, orange, yellow, green, blue, indigo, and violet. and violet.

Color Temperature is a scale that compares the Color Temperature is a scale that compares the various colors of light to the changes in color of a various colors of light to the changes in color of a black body as its temperature is increased. black body as its temperature is increased.

While brightness of light is important, one’s ability While brightness of light is important, one’s ability to visually distinguish objects rests more with the to visually distinguish objects rests more with the amount of amount of contrastcontrast of light between the objects. of light between the objects.

COLOR TEMPERATURECOLOR TEMPERATURE

The varying hues of light color is a The varying hues of light color is a comparison of the colors that appear on a comparison of the colors that appear on a black body when heated to various black body when heated to various temperatures. A physicist, William Kelvin temperatures. A physicist, William Kelvin heated a block of carbon, which first heated a block of carbon, which first produced a dim red light, increasing to a produced a dim red light, increasing to a brighter yellow as the temperature brighter yellow as the temperature increased, and eventually produced a increased, and eventually produced a bright blue-white glow at the highest bright blue-white glow at the highest temperature.temperature.

Since absolute zero temperature is minus Since absolute zero temperature is minus 273 degrees Celsius, that is the zero, or 273 degrees Celsius, that is the zero, or beginning point on the Kelvin scale. So beginning point on the Kelvin scale. So the temperature at which water freezes is the temperature at which water freezes is 273 degrees Kelvin. The color 273 degrees Kelvin. The color temperature of various light sources is temperature of various light sources is important in architectural design. important in architectural design.

The Kelvin ScaleThe Kelvin Scale– TemperatureTemperature Light sourceLight source

– 1500 – 18001500 – 1800 Candle flameCandle flame– 20002000 SunriseSunrise– 2000 – 30002000 – 3000 Incandescent lampsIncandescent lamps– 35003500 Tungsten halogen Tungsten halogen

lamplamp– 3000 – 42003000 – 4200 Standard FluorescentStandard Fluorescent– 55005500 Noon sunlightNoon sunlight– 6500 – 70006500 – 7000 Overcast skyOvercast sky– 80008000 North lightNorth light– 10,000 – 25,00010,000 – 25,000 Clear blue skyClear blue sky

LIGHTING AND ARCHITECTURAL DESIGNLIGHTING AND ARCHITECTURAL DESIGN

1 In the past, lighting design assumed 1 In the past, lighting design assumed two positions: two positions: ONEONE, to vary the intensity , to vary the intensity of light in various areas for dramatic of light in various areas for dramatic effect, and effect, and TWOTWO, bombard work areas , bombard work areas with intense light with no regard for the with intense light with no regard for the actual actual needsneeds of visual tasks. of visual tasks.

2 Responsible lighting design demands 2 Responsible lighting design demands the considerations of dramatic aesthetic the considerations of dramatic aesthetic effects, plus two aspects in the workplace effects, plus two aspects in the workplace to meet the physiological needs ofto meet the physiological needs of quantityquantity, and , and

quality quality

of light for given tasks: of light for given tasks:

THE ASPECT OF THE ASPECT OF QUANTITYQUANTITY

1 Consideration of daylight, 1 Consideration of daylight, supplemented by artificial sources. supplemented by artificial sources. Introduction of full spectrum light.Introduction of full spectrum light.

2 The relationship of energy between 2 The relationship of energy between lighting and comfort heating and cooling. lighting and comfort heating and cooling. Intensifying one at the expense of the Intensifying one at the expense of the other.other.

3 The effect of lighting on space 3 The effect of lighting on space arrangements. Evenness and contrast arrangements. Evenness and contrast ratios where needed.ratios where needed.

4 The visual needs of specific occupants. 4 The visual needs of specific occupants. Light and contrast at specific places. Light and contrast at specific places.

THE ASPECT OF THE ASPECT OF QUALITYQUALITY

1 Physiological expressions of brightness 1 Physiological expressions of brightness ratio. Eyestrain from too much or too ratio. Eyestrain from too much or too little.little.

2 Consideration of color. Not only of 2 Consideration of color. Not only of light, but that of illuminated surfaces.light, but that of illuminated surfaces.

3 Artistic effects in aesthetic 3 Artistic effects in aesthetic considerations. Enhancements of considerations. Enhancements of architectural accouterments.architectural accouterments.

4 Light in task areas with extended 4 Light in task areas with extended periods of time. Intensity and direction of periods of time. Intensity and direction of illumination.illumination.

All of which are essential in All of which are essential in understanding the essentials in understanding the essentials in architectural rendition of lighting designarchitectural rendition of lighting design. .

Artificial lighting is adequate in Artificial lighting is adequate in quantity – but it takes the benefits of full quantity – but it takes the benefits of full spectrum color in light to satisfy the spectrum color in light to satisfy the physiological aspects of quality. physiological aspects of quality.

LIGHT, VISION, AND THE HUMAN EYELIGHT, VISION, AND THE HUMAN EYE

The Basic Form of the EyeThe Basic Form of the Eye

1 Vision happens through multiple 1 Vision happens through multiple parts working together to cause a visual parts working together to cause a visual sensation.sensation.

2 The principal parts are the cornea, 2 The principal parts are the cornea, pupil, lens, transparent fluid, (vitreous pupil, lens, transparent fluid, (vitreous humor) the retina, optic nerve, and of humor) the retina, optic nerve, and of course, the brain.course, the brain.

IMPAIRMENTS TO SIGHTIMPAIRMENTS TO SIGHT

Ever heard someone ask, “How far can Ever heard someone ask, “How far can you see?” Actually, a misnomer, since the you see?” Actually, a misnomer, since the eye must focus clearly on some object eye must focus clearly on some object from which reflected light enters the eye. from which reflected light enters the eye. The strength of the eye does not project The strength of the eye does not project some power to reach out to an object, but some power to reach out to an object, but rather how it perceives the image rather how it perceives the image impressed on the retina.impressed on the retina.

The power of eyesight varies between The power of eyesight varies between humans, animals, birds, and insects – not humans, animals, birds, and insects – not all have the same quality to detect visual all have the same quality to detect visual images. images.

ALTERATIONS TO THE LIGHT PATHALTERATIONS TO THE LIGHT PATH

Chances are you have heard the Chances are you have heard the terms, ‘terms, ‘farsightedfarsighted, , nearsightednearsighted, , astigmatismastigmatism, or, or cataractscataracts. Terms that . Terms that describe some variation in one or more describe some variation in one or more parts of the eye, different from that of a parts of the eye, different from that of a normal, healthy eye, that alters the normal, healthy eye, that alters the course of light into the mechanism.course of light into the mechanism.

And chances are you do, or know And chances are you do, or know someone who wears corrective glasses to someone who wears corrective glasses to redirect the path of light. redirect the path of light. Me, for Me, for instanceinstance. I’ve been described a lot worse . I’ve been described a lot worse than ‘abnormal.’than ‘abnormal.’

ASTIGMATISMASTIGMATISM

The cornea is the transparent cover The cornea is the transparent cover over the outside of the eyeball. It’s like a over the outside of the eyeball. It’s like a sheet of plastic over the hole that allows sheet of plastic over the hole that allows light inside. light inside.

If If the cornea is slightly warpedthe cornea is slightly warped, the , the condition might cause the visual sensation condition might cause the visual sensation to appear as a warped mirror, distorting to appear as a warped mirror, distorting the object that is reflected.the object that is reflected.

Corrective lenses are designed to Corrective lenses are designed to straighten out the warp as the light passes straighten out the warp as the light passes through.through.

IIFARSIGHTEDFARSIGHTED doesn’t mean one can see a doesn’t mean one can see a long way.long way.

Ideally, the light rays that enter the Ideally, the light rays that enter the pupil are bent by the lens to focus exactly pupil are bent by the lens to focus exactly on the retina at the back of the eyeball.on the retina at the back of the eyeball.

In the case of farsightedness, the In the case of farsightedness, the natural lens is too flat and the light focal natural lens is too flat and the light focal length is well beyond the retina, or length is well beyond the retina, or the the focal length is too longfocal length is too long, Hence the term, , Hence the term, farsighted, properly called ‘farsighted, properly called ‘hyperopiahyperopia.’.’

To correct the lens with laser surgery, To correct the lens with laser surgery, attempts to shave off a small portion of the attempts to shave off a small portion of the edge of the lens and make the curvature edge of the lens and make the curvature greater. The process is very difficult.greater. The process is very difficult.

NEARSIGHTEDNEARSIGHTED Does not mean one can’t see very Does not mean one can’t see very far.far.

The cause of nearsightedness is the opposite The cause of nearsightedness is the opposite that of farsightedness, in that that of farsightedness, in that the length from the length from the lens to the point of focus is too shortthe lens to the point of focus is too short. The . The visual image comes into focus before it gets to visual image comes into focus before it gets to the retina.the retina.

This is caused by the lens being too rounded, This is caused by the lens being too rounded, and the process of correction by laser surgery is and the process of correction by laser surgery is to shave off a small portion of the top of to shave off a small portion of the top of curvature to make the lens a little flatter. Lasik curvature to make the lens a little flatter. Lasik is an acronym for Laser Assisted in Situ is an acronym for Laser Assisted in Situ Keratomileusis Keratomileusis

Nearsightedness, called Nearsightedness, called ‘myopia’‘myopia’ is far more is far more prevalent in humans than is farsightedness. prevalent in humans than is farsightedness.

CATARACTSCATARACTS

Cataracts are a clouding of the natural Cataracts are a clouding of the natural lens of the eye. Since the lens acts similar lens of the eye. Since the lens acts similar to a magnifying glass to bend the direction to a magnifying glass to bend the direction of light rays to the focal point, it must be of light rays to the focal point, it must be completely transparent. completely transparent.

The situation is not caused by aging, The situation is not caused by aging, but because it takes time to occur, most but because it takes time to occur, most cataract surgery takes place when one is cataract surgery takes place when one is older. Cataracts are not automatic with older. Cataracts are not automatic with age.age.

In cataract correction, the surgeon In cataract correction, the surgeon simply cuts a slit at the top of the eyeball, simply cuts a slit at the top of the eyeball, removes the clouded lens, and inserts an removes the clouded lens, and inserts an artificial lens of desired curvature, then artificial lens of desired curvature, then sutures the slit. sutures the slit.

GLAUCOMAGLAUCOMA

The eyeball is filled with a liquid called The eyeball is filled with a liquid called vitreous humor, manufactured by the body, vitreous humor, manufactured by the body, introduced into the eye through a tiny sieve. introduced into the eye through a tiny sieve. In normal conditions, fluid is forced out the In normal conditions, fluid is forced out the back through a tiny sieve, and absorbed into back through a tiny sieve, and absorbed into the body.the body.

When the fluid exhaust is impaired, When the fluid exhaust is impaired, pressure inside the ball increases, and if not pressure inside the ball increases, and if not corrected, causes blindness.corrected, causes blindness.

A laser beam can be directed to the A laser beam can be directed to the outlet duct to open the impairment and outlet duct to open the impairment and relieve pressure. A more effective way is to relieve pressure. A more effective way is to surgically cut a small “controlled” hole in the surgically cut a small “controlled” hole in the top of the eyeball inside the socket, so fluid top of the eyeball inside the socket, so fluid can seep out and be absorbed by the body.can seep out and be absorbed by the body.

MACULA DEGENERATIONMACULA DEGENERATION

The macula lutea is a spot at the back The macula lutea is a spot at the back of the inside of the eyeball where light of the inside of the eyeball where light focuses to create the most acute focuses to create the most acute sensations that result in vision.sensations that result in vision.

The macula is rather like a computer The macula is rather like a computer screen, in that the tiny nerves are screen, in that the tiny nerves are connected, similar to pixels, or points of connected, similar to pixels, or points of sensitivity – sort of like “resolution of the sensitivity – sort of like “resolution of the eye.” Think of how many dots it takes to eye.” Think of how many dots it takes to make a picture.make a picture.

If this membrane begins to be If this membrane begins to be damaged, and close nerve endings, then damaged, and close nerve endings, then less and less visual sensation occurs. It less and less visual sensation occurs. It can happen in various areas of the macula, can happen in various areas of the macula, and if unchecked, blindness occurs. There and if unchecked, blindness occurs. There is no known cure for macula degeneration.is no known cure for macula degeneration.

OPTIC ATROPHYOPTIC ATROPHY

At the back of the eyeball where the At the back of the eyeball where the macula occurs, hundreds of nerves connect macula occurs, hundreds of nerves connect for the purpose to transferring the visual for the purpose to transferring the visual sensation through the collected bundle sensation through the collected bundle called the optic nerve.called the optic nerve.

The optic nerve is much like a bundle The optic nerve is much like a bundle of fiber optic cables, transferring each tiny of fiber optic cables, transferring each tiny pixel that make up a visual sensation to pixel that make up a visual sensation to create an image in the brain.create an image in the brain.

If these tiny nerves deteriorate If these tiny nerves deteriorate gradually over a period of time, blindness gradually over a period of time, blindness can occur. While there are precautions can occur. While there are precautions against optic atrophy, there is no known against optic atrophy, there is no known cure. cure.

THE MEASUREMENT OF LIGHTTHE MEASUREMENT OF LIGHT

BASIC ILLUMINATIONBASIC ILLUMINATION

1 Luminous Flux: The force of light energy 1 Luminous Flux: The force of light energy on a surface. on a surface.

2 2 CandlepowerCandlepower: The unit of luminous : The unit of luminous intensity. The amount of light on one square intensity. The amount of light on one square foot on the surface of a transparent sphere foot on the surface of a transparent sphere from a standard wax candle at the center from a standard wax candle at the center produces one produces one LUMENLUMEN..

3 The Units of Measurement:3 The Units of Measurement:

One lumen on one square foot equals one One lumen on one square foot equals one FOOTCANDLE FOOTCANDLE (English Measurement) (English Measurement)

One lumen on one square meter equals one One lumen on one square meter equals one LUXLUX. .

(Scientific Measurement)(Scientific Measurement)

A footcandle and a Lux have the same A footcandle and a Lux have the same amount of light in lumens.amount of light in lumens.

A square foot is 12” x 12”. A square A square foot is 12” x 12”. A square meter is 39.37” x 39.37”. A square meter meter is 39.37” x 39.37”. A square meter is 10.76 times larger than a square foot. is 10.76 times larger than a square foot.

Each area has the same amount of Each area has the same amount of light.light.

Therefore, a FOOTCANDLE is 10.76 Therefore, a FOOTCANDLE is 10.76 times times brighter than a LUX.brighter than a LUX.

Artificial Lighting SourcesArtificial Lighting Sources

Although numerous types of lighting sources exist Although numerous types of lighting sources exist today, today, for the most part the design of buildings for the most part the design of buildings involves only three.involves only three.The three major types of lamps utilized in building The three major types of lamps utilized in building construction are,construction are,

IncandescentIncandescentFluorescentFluorescentHigh Intensity DischargeHigh Intensity Discharge

While While neonneon is a lighting source, it is is a lighting source, it is primarily a device utilized in color décor and primarily a device utilized in color décor and signage, rather than illumination. signage, rather than illumination.

This study in lighting design involves This study in lighting design involves general architectural area lighting, such as general architectural area lighting, such as might be required for work areas.might be required for work areas.

Special illumination such as stage Special illumination such as stage lighting, showcases, artistic effects, and lighting, showcases, artistic effects, and for exterior area lighting in arenas and for exterior area lighting in arenas and parking lots are all highly specialized parking lots are all highly specialized subjects, and are specific studies in subjects, and are specific studies in themselves.themselves.

General area lighting involves not only General area lighting involves not only direct light from a source, but depends direct light from a source, but depends upon reflection, maintenance, and the upon reflection, maintenance, and the specific way lighting units are utilized. specific way lighting units are utilized. Manufacturing laboratory data is available Manufacturing laboratory data is available for general area lighting in how their units for general area lighting in how their units are utilized. are utilized.

INDIRECT LIGHTING, such as lighting INDIRECT LIGHTING, such as lighting units directed upward to a reflective units directed upward to a reflective ceiling, and lighting installed in a ceiling, and lighting installed in a continuous cove are mainly for special continuous cove are mainly for special effects and general illumination rather effects and general illumination rather than for specific tasks.than for specific tasks.

Uplight and cove lighting is very Uplight and cove lighting is very inefficient from the standpoint of lumens inefficient from the standpoint of lumens per watt, as a large amount of the light is per watt, as a large amount of the light is lost in the surrounding elements. But the lost in the surrounding elements. But the advantage of the two types lies in a very advantage of the two types lies in a very evenly distributed soft area light.evenly distributed soft area light.

A building code that restricts the A building code that restricts the amount of energy used for lighting will amount of energy used for lighting will severely restrict the amount of indirect severely restrict the amount of indirect lighting in public places.lighting in public places.

A THE INCANDESCENT LAMPA THE INCANDESCENT LAMP

The word The word ‘incandescent’‘incandescent’ means to means to emit light as the result of being heated.emit light as the result of being heated.

Edison did not have a problem finding Edison did not have a problem finding materials that would glow when subjected materials that would glow when subjected to an electrical current, thus producing to an electrical current, thus producing bright light. His problem was finding the bright light. His problem was finding the combination of material within a specific combination of material within a specific atmosphereatmosphere that would glow white hot for that would glow white hot for a long period of time. a long period of time.

It took 10,005 tries before he finally It took 10,005 tries before he finally got it. got it.

1 The Common Incandescent Light Bulb 1 The Common Incandescent Light Bulb

consists of a consists of a glass enclosureglass enclosure, of which the , of which the air inside has been replaced by air inside has been replaced by inert inert gassesgasses that will not support combustion – that will not support combustion – a a metal filamentmetal filament sealed inside that sealed inside that artificial atmosphere can withstand very artificial atmosphere can withstand very high temperature. high temperature.

The ends of the metal filament extend The ends of the metal filament extend to separate electrical contacts which to separate electrical contacts which transfers electrical current directly to the transfers electrical current directly to the filament and filament and resist heat as a direct resist heat as a direct electrical shortelectrical short. In electrical terms, the . In electrical terms, the filament is a direct short to the electrical filament is a direct short to the electrical current.current.

The standard incandescent The standard incandescent light bulblight bulb like you see in any normal household lamp, is like you see in any normal household lamp, is made up of a fairly large, thin, glass envelope. made up of a fairly large, thin, glass envelope. Inside the glass is a gas such as argon and/or Inside the glass is a gas such as argon and/or nitrogen. nitrogen.

At the center of the lamp is a At the center of the lamp is a tungsten filament. Electricity heats this tungsten filament. Electricity heats this filament to about 4,500 degrees F. Just filament to about 4,500 degrees F. Just like any hot metal, the tungsten gets like any hot metal, the tungsten gets "white hot" at that heat and emits a great "white hot" at that heat and emits a great deal of deal of visible lightvisible light in a process called in a process called incandescence. incandescence.

A normal light bulb is not very efficient, A normal light bulb is not very efficient, and it only lasts about 750 to 1,000 hours in and it only lasts about 750 to 1,000 hours in normal use. It's not efficient because, in the normal use. It's not efficient because, in the process of radiating light, it also radiates a process of radiating light, it also radiates a huge amount of infrared heat -- far more huge amount of infrared heat -- far more heat than light. heat than light.

Since the purpose of a light bulb is to Since the purpose of a light bulb is to generate light, the heat is wasted energy. It generate light, the heat is wasted energy. It doesn't last very long because the tungsten doesn't last very long because the tungsten in the filament evaporates and deposits on in the filament evaporates and deposits on the glass, hence the black spot on a burnt-the glass, hence the black spot on a burnt-out bulb. Eventually, a thin spot in the out bulb. Eventually, a thin spot in the filament causes the filament to break, and filament causes the filament to break, and the bulb "burns out." the bulb "burns out."

2 The Tungsten Halogen Bulb – developed 2 The Tungsten Halogen Bulb – developed 1980s1980s

Is an incandescent source much like the Is an incandescent source much like the previous, as previous, as the filament is made of the filament is made of tungstentungsten. The inside of the bulb is filled with . The inside of the bulb is filled with a combination of gas chemical from the a combination of gas chemical from the halogenshalogens..

The The ‘halogens’ is a chemical group ‘halogens’ is a chemical group consisting of iodine, bromide, chlorine, consisting of iodine, bromide, chlorine, astatine, and fluorineastatine, and fluorine,, the proper the proper combination of which, contributes to a combination of which, contributes to a brighter and longer lamp life.brighter and longer lamp life.

The Tungsten Halogen is a smaller unit, The Tungsten Halogen is a smaller unit, and and the glass enclosure is made of quartzthe glass enclosure is made of quartz, ,

The filament of a halogen lamp is The filament of a halogen lamp is encased inside a much smaller quartz tube. encased inside a much smaller quartz tube. Because the envelope is so close to the Because the envelope is so close to the filament, it would melt if it were made of filament, it would melt if it were made of ordinary glass. ordinary glass.

The The halogenhalogen gases inside have a very gases inside have a very interesting property: They combine with interesting property: They combine with tungsten vapor. If the temperature is high tungsten vapor. If the temperature is high enough, the halogen gas will combine with enough, the halogen gas will combine with tungsten tungsten atomsatoms as they evaporate due to heat, as they evaporate due to heat, and redeposit them on the filament. This recycling and redeposit them on the filament. This recycling process lets the filament last much longer. In process lets the filament last much longer. In addition, it is now possible to run the filament addition, it is now possible to run the filament hotter, meaning you get more light per unit of hotter, meaning you get more light per unit of energy, but the unit is extremely hot compared to energy, but the unit is extremely hot compared to a normal light bulb. a normal light bulb.

A 100 WATT TUNGSTEN HALOGEN BULBThe glass housing the filament is approximately one inch long

B THE FLUORESCENT LAMPB THE FLUORESCENT LAMP

The fluorescent lamp consists of The fluorescent lamp consists of 4 basic 4 basic partsparts::

– The glass tubeThe glass tube – varies in length and – varies in length and diameter, diameter, coated inside with a coated inside with a phosphorescent materialphosphorescent material..

– Mercury vapor gasMercury vapor gas sealed inside. sealed inside.– Sealed Sealed electrodeelectrode at each end at each end

– Electrical current causes electrons to be Electrical current causes electrons to be released from the electrodes, which collide released from the electrodes, which collide with mercury atoms, causing them to emit with mercury atoms, causing them to emit ultraviolet light, invisible to the human ultraviolet light, invisible to the human eye. eye.

The phosphorescent coating reacts The phosphorescent coating reacts with the UV rays and changes the with the UV rays and changes the frequency of the UV to the “visible” light frequency of the UV to the “visible” light range.range.

But even though the light is in the But even though the light is in the visible range, it is far from full spectrum visible range, it is far from full spectrum light that contains all the colors of natural light that contains all the colors of natural light. Standard, “cool white” fluorescent light. Standard, “cool white” fluorescent tubes emit light in the middle of the tubes emit light in the middle of the spectrum, resulting in a greenish color. spectrum, resulting in a greenish color.

Many color corrected fluorescent Many color corrected fluorescent lamps are available that have produced a lamps are available that have produced a warmer type of light.warmer type of light.

A fluorescent light source A fluorescent light source produces less heat, so it is much produces less heat, so it is much more efficient from the standpoint of more efficient from the standpoint of lumens per watt of power. A lumens per watt of power. A fluorescent bulb can produce fluorescent bulb can produce between 50 and 100 lumens per watt. between 50 and 100 lumens per watt. This makes fluorescent bulbs four to This makes fluorescent bulbs four to six times more efficient than six times more efficient than incandescent bulbs. incandescent bulbs.

That is why a 15-watt fluorescent That is why a 15-watt fluorescent bulb can produce the same amount of bulb can produce the same amount of light as a 60-watt incandescent bulb. light as a 60-watt incandescent bulb.

Compact Fluorescent LampsCompact Fluorescent LampsCOMPACT FLUORESCENT LAMPS

C HIGH INTENSITY DISCHARGEC HIGH INTENSITY DISCHARGE

A high pressure lamp that A high pressure lamp that utilizes metallic utilizes metallic vapors insidevapors inside, , to react with electrons to react with electrons within a arc enclosurewithin a arc enclosure. .

Contents are under high pressure and Contents are under high pressure and heat, which results in a need for a thicker heat, which results in a need for a thicker outer glass enclosure.outer glass enclosure.

Three main types includeThree main types include– MercuryMercury Vapor Vapor– SodiumSodium Vapor Vapor– Metal HalideMetal Halide – a salt derived from the – a salt derived from the

‘halogens’‘halogens’

Inside the outer bulb enclosure, Inside the outer bulb enclosure, electrodes are connected to a sealed tube electrodes are connected to a sealed tube of polychrystalline aluminaof polychrystalline alumina, in which is , in which is xenon gasxenon gas. On startup the electrodes cause . On startup the electrodes cause a continuous electrical arc within the gas, a continuous electrical arc within the gas, which heats the tube and ionizes gas within which heats the tube and ionizes gas within the tube. (mercury, sodium, or halide)the tube. (mercury, sodium, or halide)

As soon as the arc is established, the As soon as the arc is established, the startup voltage is switched off by the startup voltage is switched off by the ballast, and the ionization of the gas in the ballast, and the ionization of the gas in the tube continues until full brightness is tube continues until full brightness is achieved.achieved.

The electrical ballast controls the The electrical ballast controls the amount of voltage within the arc, which in amount of voltage within the arc, which in turn, controls the proper amount of current turn, controls the proper amount of current for optimum operation.for optimum operation.

1 1 Mercury VaporMercury Vapor : 1960s, the first type : 1960s, the first type developed. Light has definite greenish developed. Light has definite greenish color. Lamp life upwards to 24,000 hourscolor. Lamp life upwards to 24,000 hours

2 2 Sodium LampsSodium Lamps : 1970s Light has a : 1970s Light has a yellow to orange color. Lamp life upwards yellow to orange color. Lamp life upwards to 24,000 hours.to 24,000 hours.

3 3 Metal HalideMetal Halide : 1980 Light is very white, : 1980 Light is very white, and is usable indoors for special and is usable indoors for special applications. Lamp life upwards to 15,000 applications. Lamp life upwards to 15,000 hours. The lamp, unlike mercury and hours. The lamp, unlike mercury and sodium, must be placed inside a glass sodium, must be placed inside a glass protective enclosure, because of the danger protective enclosure, because of the danger of explosion.of explosion.

Quartz outer bulb with argon Quartz outer bulb with argon gas.gas.

electrodeelectrode

polychrystalline alumina polychrystalline alumina tube with xenon gas plus tube with xenon gas plus either mercury, sodium, or either mercury, sodium, or metal halide.metal halide.

electrodeelectrode

EFFICIENCY COMPARISON OF LAMPSEFFICIENCY COMPARISON OF LAMPS

Incandescent: 100 watt, 1700 lumens = Incandescent: 100 watt, 1700 lumens = 1717 lumens/wattlumens/watt. Life = 750 hours. Cost is . Life = 750 hours. Cost is less less than one dollarthan one dollar..

Fluorescent: 40 watt tube, 3200 lumens = Fluorescent: 40 watt tube, 3200 lumens = 8080 lumens per wattlumens per watt. Life is 12,000 – 20,000 . Life is 12,000 – 20,000 hours. Cost is hours. Cost is two to four dollarstwo to four dollars..

HID : 100 watts, 7500 – 9000 lumens = HID : 100 watts, 7500 – 9000 lumens = 75 – 75 – 9090 lumens per wattlumens per watt. Life = 20,000 hours. . Life = 20,000 hours. Cost of a 100 watt lamp is approximately Cost of a 100 watt lamp is approximately thirty dollarsthirty dollars..

D NEON LIGHTINGD NEON LIGHTING

““Neon” lighting is actually not a method of Neon” lighting is actually not a method of illumination task lighting, but one of décor illumination task lighting, but one of décor and advertising.and advertising.

Inside a glass tube is a gas like neon, Inside a glass tube is a gas like neon, krypton, argonkrypton, argon, etc. At both ends of the , etc. At both ends of the tube are electrodes. An tube are electrodes. An electrical charge electrical charge causes the gas to ionizecauses the gas to ionize, and electrons flow , and electrons flow through the gas. These electrons excite through the gas. These electrons excite the atoms of the gas and cause them to the atoms of the gas and cause them to emit light that is visible to the human eye.emit light that is visible to the human eye.

The color of the light depends upon the gas The color of the light depends upon the gas or mixture of gas in the tubeor mixture of gas in the tube. .

Of special note, Of special note, what is the source of what is the source of light on the screen of your laptop light on the screen of your laptop computer?computer? Special material, called “liquid Special material, called “liquid crystals” activate images when excited by crystals” activate images when excited by an electrical current – through a complex an electrical current – through a complex polarizing process. The display without polarizing process. The display without help is not light emitting, such as with help is not light emitting, such as with Light Emitting Diodes. Light Emitting Diodes.

So in the case of your LCD computer So in the case of your LCD computer monitor or television, the liquid crystal monitor or television, the liquid crystal display is illuminated by fluorescent tubes display is illuminated by fluorescent tubes above, beside and sometimes behind the above, beside and sometimes behind the LCD. A white diffusion panel behind the LCD. A white diffusion panel behind the LCD redirects and scatters the light evenly LCD redirects and scatters the light evenly to ensure a uniform display. to ensure a uniform display.

FLUORESCENTTUBE FOR BACKLIGHTINGIN A LAPTOP COMPUTER

LIQUID CRYSTALS are made from polymers.LIQUID CRYSTALS are made from polymers.

If a polymer is heated to a certain If a polymer is heated to a certain temperature, the mass changes to a liquid crystal temperature, the mass changes to a liquid crystal state – neither liquid or solid, but rather like gel. state – neither liquid or solid, but rather like gel. Once the crystal state is formed, it remains. Once the crystal state is formed, it remains.

The molecular structure of the material is The molecular structure of the material is rod-like, and in the crystal state become parallel, rod-like, and in the crystal state become parallel, and can be influenced by electrical current to and can be influenced by electrical current to produce visual images. If liquid crystals are produce visual images. If liquid crystals are heated further, they will turn to liquid.heated further, they will turn to liquid.

Liquid crystals are somewhat sensitive to Liquid crystals are somewhat sensitive to heat and cold and your display may do strange heat and cold and your display may do strange things on a hot, summer day outside, or after things on a hot, summer day outside, or after having been left in a closed automobile.having been left in a closed automobile.

Similar results may occur if you take your Similar results may occur if you take your laptop on a ski trip, and do your environmental laptop on a ski trip, and do your environmental systems research sitting on the top of a systems research sitting on the top of a mountain surrounded by snow. mountain surrounded by snow.

Most all commercial electronic equipment Most all commercial electronic equipment state a safe operating temperature range as a state a safe operating temperature range as a disclaimer for its performance. disclaimer for its performance.