illumination basic and schemes (1)

7/25/2019 Illumination Basic and Schemes (1)

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Topics

1. Introduction2. Nature of light

3. Terms used in illumination

4. Law of illumination5. Electrical methods of producing light

6. ources of light

!. "rc lamps

#. $ilament lamps

%. &aseous discharge lamps


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Topics1'.odium (apor lamp

11.)ercur* (apor lamp

12.$luorescent tu+e

13.Neon lamp

14.,alogen lamp

15.-ompact uorescent lamp

16.-andle power and its measurement1!.Lighting scheme

1#.treet light

1%.$lood lighting


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Introduction"s we /now that almost all human acti(ities

depends on light. un is a prime naturalsource of light +ut arti0cial lighting pla*salmost main role in our dail* life. These

arti0cial lights are produced +*mechanical lamps and electrical lamps.

ut due to poor performance themechanical light are totall* replaced +*electrical lights. The electrical lightingare mainl* used for decorati(e purposead(ertising trac control medical 0eld

and street lighting etc.


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Electrical LightingElectrical lighting has following

ad(antages

1. -leanliness

2. Eas* to control

3. Economical

4. Eas* to handle

5. tead* output6. etter relia+ilit*

!. uita+le for almost all purposes etc.


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ensiti(it* of ,uman E*e

"s we /now natural light consists of se(encolors ha(ing dierent wa(elengths. Thea(erage human e*e is most sensiti(e to a

wa(e length of 55'' '".The relati(e sensiti(it* of e*e for a

particular wa(e length is the (isual eectproduced +* the light on the a(eragehuman e*e as compared with the eect oflight ha(ing wa(e length 55'' '" onhuman e*e.


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Sensitivity of Human eye

This is also /nown as elati(eluminosit* $actor.


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Terms used in Illumination1. Light

2. Luminous u7

3. Lumen

4. 8lane angle

5. olid angle

6. teradian

!. -andle power#. Luminous intensit* reduction factor

%. &lare

1'.Lamp ecienc*


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light

That part of radiant energ*from a hot +od* which

produced the (isualsensation on human e*e is

called light.


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Luminous $lu7

The total 9uantit* of radiantenerg* per secondresponsi+le for (isual

sensation from a luminous+od* is called Luminous $lu7.

It is represented as $ of : andmeasured in lumens.


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Lumen

It is the unit of luminous u7.;ne lumen is de0ned as the

luminous u7 emitted perunit solid angle from a pointsource of one candle power.

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Plane AngleThe angle su+tended at a point +* two con(erging lines l*ing inthe same plane is called plane angle. It is measured in radians ande9ual to the ratio of the length of the arc too its radius

= > arc< radius > l< r radians11


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Solid AngleThe angle su+tended +* the partial surface area of a sphere at itscentre is called as solid angle. It is measured in steradians and e9ualto the ratio of area of the surface to the s9uare of radius of sphere

? > area of surface< s9uare of radius > "< r2 steradians11


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teradian

the unit of solid angle. ;nesteradian is de0ned as the solidangle that is su+tended at thecentre of a sphere +* its surfaceha(ing area e9ual to radiuss9uare

? > surface area< @radiusA2

> r 2< r2> 1 steradian


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-andle 8ower

The light radiating capacit* of asource is called its candle power.The num+er of lumens gi(en out +*

a source per unit solid angle in agi(en direction is called its candlepower. It is denoted +* -.8.

Total u7 emitted > -8 B solid angle> 1 B 4C > 4C lumens

> 4C lumens


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Luminous Intensit*

Luminous intensit* in an*particular direction is the luminousu7 emitted +* the source per unit

solid angle in that direction. It is denoted +* I and its unit is

candela or candle power @-8A .

Luminous intensit* of source in aparticular direction I > D < ?

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eduction $actor

reduction factor of a source oflight is the ratio of its meanspherical candle power to its

mean horiontal candle power.

eduction factor > )-8< ),-8

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Illumination

Fhen light falls on a surface it+ecomes (isi+le the phenomenonis called as illumination.

It is de0ned as luminous u7 fallingon a surface per unit area. It isdenoted +* E and measured in

lumen per s9uare meter or meterGcandle.

E > H < " lu7

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Lu7

;ne meter candle or lu7 is de0nedas the illumination produced +* a

uniform souce of one -8 on theinner surface of a sphere ofradius one meter.


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&lareIn the human e*e the opening of pupil is

controlled +* its iris which depends upon theintensit* of light recei(ed +* the e*e. If thee*e is e7posed to a (er* +right source oflight the pupil of the e*e contracts

automaticall* in order to reduce the amountof light admitted and pre(ent damage to theretina. This eect is called glare.

&lare is de0ned as the +rightness within the0eld of (ision of such a character so as tocause discomfort and interference in (ision.


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Lamp Ecienc*It is de0ned as the (isi+le radiations

emitted +* it in lumens per watt.suall* the light sources do not radiate

energ* onl* in the (isi+le spectrum.

The radiant energ* is alsoaccompanied with infrared and ultra(iolet radiations.

un light produces maJorit* of radiationsin the (isi+le spectrum. The tungstenlamp produces small radiations so its

ecienc* is (er* poor.


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Lamp eciency

The ecienc* of uorescent lamp ismore than tungsten lamp.


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eection $actor

Fhole of the light incident on areecting surface is not reected.ome portion of it is a+sor+ed +* thesurface.

The ratio of the reected light to theincident light is called reectionfactor.


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Law of Illumination

The illumination on a surface dependsupon the luminous intensit* distance+etween the source and surface andthe direction of ra*s of light. It isgo(erned +* following laws

1.In(erse s9uare law

2.Lam+ertKs cosine law

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Inverse Square LawIt states that the illumination of a surface isin(ersel* proportional to the s9uare of the distance

of the surface from the source. E 1


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Lamberts CosineLaw

This law states that the illumination on an* surface isproportional to the cosine of angle +etween the direction of theincident u7 and perpendicular to the area. E > 1


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Electrical method ofproducing Light

$ollowing are the methods of producinglight

1.* de(eloping arc +etween twoelectrodes

2.* passing a current through a 0lament

3.* electric discharge through (apors orgases


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"rc Lamp

The principle of an arc lamp is that whentwo electrodes carr*ing current areseparated through a small distance anarc is struc/ +etween them. The arc

lamps were used in the past for streetlighting purposes +ut now a da* theseare used when e7treme +rightness is

re9uired.)ost commonl* use arc lamp is

-ar+on "rc Lamp


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-ar+on "rc Lamp This is the oldest t*pe of lamp and is still

+eing emplo*ed in cinema proJectors andsearch lights. It consists of two hardcar+on rods @ElectrodesA. The diameter ofM(e electrode is dou+le to that of (e

electrode. The (e electrode is generall*07ed and M(e electrode is placed inadJusta+le holder and the process ismanuall* or automatic. The arc consists ofcar+on (apors surrounded +* orange redone of +urning car+on and pale greenames.


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-ar+on "rc LampFhen the lamp is ;$$ the two electrodes are

touching each other due to spring pressureon M(e electrode. Fhen the suppl* is ;N alarge current is ow through electrodes. Thetemperature of car+on electrode is increased

and thus the M(e electrode is pulled awa*against its spring pressure through a smalldistance +* coil and thus an arc is struc/

+etween electrodes. This arc is maintained+* transfer of car+on particles from oneelectrode to other electrode.


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-ar+on "rc LampThese particles tra(el from M(e electrode to

(e electrode thus after sometime ofoperation M(e electrode +ecome hollow and(e +ecome pointed. ThatKs wh* M(eelectrode is made dou+le than (e electrode.

In car+on arc lamp #5 O of light is gi(en +*M(e electrode which produces high intensit*light and onl* 1' O +* (e electrode and 5 O

+* air. The temperature of M(e electrode is4''' o- and that of (e electrode is a+out25'' o-. The luminous ecienc* of suchlamps is a+out % lumen


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AC Lamps

$or maintaining the arc a minimum (oltagere9uired is gi(en +* P > @3% M 2# L A

where L is length of arc in centimeter.

amen or ncan escen


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amen or ncan escenLamp

For/ing 8rinciple

"s we /now when a room heater isswitched ;n it gi(es out red light

with heat at the wor/ing temperatureof !5' o- and at this temperature theradiations are mostl* in infra red

regions. This wor/ing principle isused to de(elop the 0lament lamp.

amen or ncan escen


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amen or ncan escenLamp

Fhen an electric current is passed

through a 0ne metallic wire it raisesthe temperature of wire. "t lowtemperature onl* heat is produced +utat higher temperature light radiationsgoes on increasing. "s 0lament lampconsists of 0ne wire of high resisti(ematerial placed in an e(acuated glass

+ul+. This t*pe of lamps are operatedat the temperature of 25'' o- .

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!ilament Lamp

" tungsten 0lament is enclosed in e(acuated glass+ul+ +ut to impro(e its performance some chemicalli/e argon or nitrogen gas are 0lled.


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8roperties of )etal for $ilament1. ,igh melting point so that it can +e

operated at high temperature.

2. ,igh speci0c resistance so that itproduces more heat.

3. Low temperature coecient so that0lament resistance ma* not change atoperating temperature.

4. Low (apor pressure Q so that it ma* not(aporie

5. ,igh ductile so that it ma* withstandmechanical (i+rations


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odium Papor Lamp

This lamp consists of discharge tu+emade from special heat resistanceglass containing a small amount ofmetallic sodium neon gas and two

electrodes. Neon gas is added to startthe discharge and to de(elop enoughheat to (aporised sodium. " long tu+e

is re9uired to get more light. To reduceo(erall dimensions of the lamp thetu+e is generall* +ent into Gshape .


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odium Papor Lamp

For/ing 8rinciple

"n electric discharge lamps re9uire a high(oltage at staring and low (oltage duringoperation. o at starting a (oltage of 45'

P is applied across the lamp to start thedischarge. "fter 1' to 15 minutes the(oltage falls to 15' P +ecause of low

power factor. To impro(e the powerfactor a capacitor is connected acrossthe suppl*. The color of light produce is*ellowish.


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odium Papor Lamp

) P L


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)ercur* Papor Lamp;n the +asis of pressure inside the discharge

tu+e the mercur* (apor lamps are classi0edas high pressure )ercur* Papor Lamp andlow pressure )ercur* Papor Lamp. ,ighpressure ).P. Lamps are of following t*pes

1.).". t*pe these are operated at 22' G25' P".-. main and made in 25' F and 4'' F.

2.).".T. t*pe these are made in 3'' and 5''

F and operated at 2'' G25' P ".-. as wellas R.-.

3.).. t*pe This is operated at 2'' 25' P".-. and made in #' F and 125 F.

) P L


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)ercur* Papor Lamp

-onstruction

It consists of hard glass tu+e enclosed in outer+ul+ of ordinar* glass. The space +etween two+ul+s are completel* e(acuated to pre(ent heatloss +* con(ection from inner +ul+. The outer +ul+

a+sor+s harmful ultra (iolet ra*s. The inner +ul+contains argon gas with certain 9uantit* ofmercur*. In addition with two electrodes onstarting electrode ha(ing high resistance in series

also pro(ided. The main electrodes are made oftungsten wire in helical shape. The lamp hasscrewed cap and connected to suppl* with cho/e." capacitor is connected across suppl* to impro(e

power factor.11


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)ercur* Papor Lamp

For/ing 8rinciple

Fhen the suppl* is switched ;N full (oltage isapplied across main and starting electrodes.This (oltage +rea/s down the gap and dischargethrough argon gas ta/es place. "s the lamp

warms up mercur* is (aporied which increasethe (apor pressure. This discharge ta/es theshape of intense arc. "fter 5 minutes the lampgi(es full light.

It gi(es greenish +lue color light .

this lamp is alwa*s suspended (erticall* otherwise inner glass tu+e ma* +rea/ due to

e7cessi(e heat.11


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)ercur* Papor Lamp

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$luorescent Tu+e

it is a low pressure mercur* (aporlamp. It consists of a glass tu+e 25mm in diameter and '.6 m 1.2 m

and 1.5 m in length. The tu+econtains argon gas at low pressurea+out 2.5 mm of mercur*. "t the two

ends two electrodes coated withsome electron emissi(e material areplaced.

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$luorescent Tu+e

The colors produce +* this tu+es are as

)aterial -olor

Sinc silicate &reen

-alcium tungstenlue

-admium +orate 8in/

-alcium ,olo phosphate Fhite or da* light

)agnesium tungsten luish white

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$luorescent Tu+e

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$luorescent Tu+e

For/ing " cho/e is connected in series with the

tu+e which act as a +allast and pro(ide

a high (oltage at starting glow in thetu+e. Ruring running condition thesame cho/e a+sor+s some suppl*(oltage and remain a (oltage of 11' P

across the tu+e. " capacitor isconnected to impro(e the power factor.

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"d(antages of $luorescentTu+e

1. Poltage uctuation has (er* smalleect on light output.

2. The luminous ecienc* is more as

length of rod is more.3. It gi(es light close to natural light.

4. ,eat radiations are negligi+le.

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Risad(antages of$luorescent Tu+e

1. Its +rightness is less.

2. Initial cost is more

3. ;(erall maintenance cost is high.

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Neon LampThese lamps are operated at a (er* low

temperature of a+out 2'' o- thatKs wh* theseare called cold cathode discharge lamps.

Two electrodes are housed at the two ends of

the tu+e which contain neon gas. Theelectrodes are made of iron or nic/el c*linderwithout an* coating and practicall* the* donot emit electrons. It gi(es red light whereas

with mi7ture of mercur* and argon it gi(es+luish green color. Poltage re9uire for startingand operation is 1'''' P. This high (oltage iso+tained from transformer.11


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Neon Lamp

For/ing

Fhen the suppl* is switched ;N at primar* sideof transformer a (oltage of 1'''' P de(elops

across secondar* side which come across twoelectrodes. "t this (oltage a discharge occursin neon gas.

Rierent colors can +e o+tained +* changingthe constituents of gases and mercur* 0lledin the tu+es.

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Neon Lamp

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Neon Lamp

"pplications

Neon lamps are generall* used forad(ertising. )ost of letters ha(ingtwo ends at which electrodes areplaced. In letter ha(ing more thantwo ends the tu+e path is repeated

for some portion.


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,alogen Lamp

,alogen lamp is a special t*pe oftungsten 0lament lamp which was

de(eloped in 1%5% in this lamps asmall amount of halogen (apor isadded to the inert gas of the +ul+. Itsglass +ul+ is small in sie andmechanicall* strong. It operates athigh temperature of 3''' o- .


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,alogen Lamp

Fhen the suppl* is gi(en to the lampa 0lament glows and produce light.

The halogen in addition to inert gascauses the e(aporated tungsten toresettle +ac/ on the 0lament duringcooling thatKs wh* lamp can +eoperated at high temperature. It

pro(ides high intensit* light.


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,alogen Lamp

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"d(antages of ,alogenLamp

1. It is smaller in sie.

2. It does not need an* +last.

3. &ood colors can +e o+tained.4. E7cellent optical control.

5. &i(es same output throughout life

6. It has long life

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Risad(antages of ,alogenLamp

1. Ruring maintenance the handling oflamp is dicult.

2. adiant heat is more which heats

the surroundings.

3. ;perating temperature is high whicheects its life.

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-ompact uorescentLamp@ -$LA

The compact uorescent lamps are+ecoming more and more popular nowa da*s +ecause of their low powerconsumption low running cost longer

life attracti(e loo/ smooth light andlow maintenance. These lamps area(aila+le in dierent sies and designs.

The* ha(e single rod dou+le rod triplerod or spiral rod. These lamps area(aila+le in dierent power rating e.g.5 ! % 11 1# and 24 watt 22' P

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-ompact uorescentLamp@ -$LA

It is +asicall* a low pressuremercur* (apor lamp ha(ing twoelectrodes coated with electron

emissi(e material placed in aglass tu+e. The tu+e is coatedinternall* with some uorescent

material in the form of powder. Inthe tu+e one drop of mercur* andargon gas is 0lled at low pressure.

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"d(antage of -$L

1. Low energ* consumption.2. Low maintenance cost

3. It stars instantl*

4. It does not heat thesurroundings

5. E7cellent color properties6. Low operating cost

!. )ore life11


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"pplications of -$L

The compact sie longer life lowrunning and maintenance costinstant glow ma/es these lamps

suita+le for all places whereuniform illumination is re9uired.

It is used in oces shops hotels

hospitals cinema hallsresidential +uildings etc.

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)easurement of -andle8ower

The candle power of a source inan* gi(en direction is

measured +* comparing it witha standard or su+standardsource with the help of an

optical instrument called8,;T;)ETE.

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8hotometer8hotometers are mostl* +ased on in(erse

s9uare law of illumination and ma* +eclassi0ed as stationar* and porta+lephotometers.

The stationar* photometers are usuall*installed in a dar/ room with dead +lac/walls and ceiling in order to eliminateerror due to reected light.

The porta+le photometers are directreading instruments used to measuredillumination in houses oces

commercial and industrial places.11


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Lighting chemesLighting schemes are classi0ed

according to the locationre9uirement and purpose etc. are asunder

1.Rirect lighting2. Indirect lighting

3.emi direct lighting

4. emi indirect lighting

5.&eneral lighting

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Rirect Lighting

"s is clear from the name in this s*stemalmost %' to %5 O light falls directl* onthe o+Ject or the surface. The light ismade to fall upon the surface with the

help of deep reectors. uch t*pe oflighting scheme is most used inindustries and commercial lighting.

"lthough this scheme is most ecient+ut it is lia+le to cause glare andshadows.

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Indirect LightingIn this s*stem the light does not fall

directl* on the surface +ut more than %'O of light is directed upwards +* usingdiusing reectors. ,ere the ceiling actsas a source of light and this light is

uniforml* distri+uted o(er the surfaceand glare is reduced to minimum. Itpro(ides shadow less illumination which

is useful for drawing oces andcomposing rooms. It is also used fordecoration purposes in cinema hallshotels etc.


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emi direct Lighting

This is also an ecient s*stem oflighting and chances of glare are also

reduced. ,ere transparent t*peshades are used through which a+out6' O light is directed downward and4' O is directed upward. This alsopro(ides a uniform distri+ution oflight and is +est suited for room withhigh ceilings.


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emi indirect Lighting

In this s*stem a+out 6' to %' O of totallight is thrown upward to the ceiling

for diused reection and the restreaches the wor/ing plane directl*. "(er* small amount of light isa+sor+ed +* the +owl. It is mainl*used for interior decoration.

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&eneral Lighting

This s*stem emplo*s such t*pe ofluminaries shades and reectors

which gi(e e9ual illumination in allthe directions.

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Resign of Indoor Lightcheme

Fhile designing a good lighting schemesthe following points must +e /ept in mind

1. It should pro(ide ade9uate illumination.

2. It should pro(ides uniforml* distri+utedlight all o(er wor/ing plane.

3. It should a(oid glare and shadows as far

as possi+le.4. It should pro(ide light of suita+le colors.

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$actors re9uired for Lightcheme

The following factors are re9uired to +econsidered while designing thelighting scheme

1. Illumination le(el2. ualit* of light

3. -o ecient of utiliation

4. Repreciation factor5. pace height ratio

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Illumination Le(el

This is the most (ital factor in decidingthe num+er and wattage ofluminaries so that we are a+le to seeand recognie the o+Ject properl*.-olors of the +od* ha(e the propert*of reecting the light in dierentproportions degree of illumination

its distance from the (iewer contrast+etween the o+Ject to +e seen andits surroundings.

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Illumination Le(el

T*pe of wor/ recommended illumination le(el;ces 1''G4'' lumens< meter s9uare

chools 25'G4'' lumens< meter s9uare

Industr* 1''' lumens< meter s9uare

hops 25'G5'' lumens< meter s9uare

,otels #'G1'' lumens< meter s9uare

,ospitals 25'G35'' lumens< meter s9uare

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ualit* of Light

This means that the illumination shouldnot +e harmful to the (iewers. It should+e glare free shadow less and contrastfree. Rirect glare from the source of

light is most common factor. 8resenceof polished and glass* surface willcause indirect glare unless diused

light is used. ,ard and long shadowscan +e a(oided +* using a largenum+er of lamps and adJusting themounting height.

- i f ili i


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-o ecient of tiliation

" surface to +e illuminated recei(e lighteither directl* from the lamps or reectedfrom the ceiling and walls or +oth. In thiscase the total u7 reaching the surface

will ne(er +e e9ual to the u7 emitted +*the lamp due to a+sorption +* reectorsceiling and walls.

tiliation factor > lumens reaching at the wor/ingplace

total lumens emitted +* the source

suall* it (aries from '.5 to '.#.

R i ti $ t


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Repreciation $actor

The total u7 emitted +* the sourceand its 0tting ma* +e reduced due todeposition of dust upon the surfaces.imilarl* 9uantit* of light reectedfrom the ceiling and walls alsodecreases with the passage of time.

This is called as depreciation facto.

suall* it (aries from 1.3 to 1.6.

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pace ,eight atio

The ratio of space @horiontal distance A+etween the two adJacent lamps to the(ertical height of the lamps a+o(e thewor/ing plane is called space height

ratio.

o the distance +etween the lamps isnot too much. "n ideal scheme could

+e when there is large num+er of smallsie lamps are used also it increasesthe cost of installation. o the spaceh i ht ti i 1 t 1 5

illumination basic and schemes (1)

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