LIGHT SOURCES ITS LIGHT SOURCES ITS ADVANTAGES & ADVANTAGES &

DISADVANTAGESDISADVANTAGES

OPTOM FASLU MUHAMMED

LIGHT SOURCESLIGHT SOURCES

Natural day lightNatural day light Electric light (artificial)Electric light (artificial)

NATURAL DAY LIGHTNATURAL DAY LIGHT Free of chargeFree of charge

Varies in quantity, colour, directions Varies in quantity, colour, directions (time of day, weather condition)(time of day, weather condition)

ELECTRIC LIGHTELECTRIC LIGHT It is constant & provided there is a It is constant & provided there is a

supply supply of electricityof electricity

LUMINOUS EFFICACYLUMINOUS EFFICACY Amount of light given by a lamp for Amount of light given by a lamp for

each watt of power consumed & is each watt of power consumed & is measured in (lumens/watt)measured in (lumens/watt)

Cannot normally operated directly Cannot normally operated directly from mains electricity supplyfrom mains electricity supply

COLOUR PROPERTIESCOLOUR PROPERTIES Related to the spectral composition Related to the spectral composition

of the emission of the emission

Include -colour rendering Include -colour rendering -colour appearance-colour appearance

COLOUR RENDERING COLOUR RENDERING

Describes the appearance of colours Describes the appearance of colours

COLOUR APPEARANCECOLOUR APPEARANCE

LAMP LIFELAMP LIFE The term ‘life’ of an electric lamp can The term ‘life’ of an electric lamp can

have two different meaningshave two different meanings

-The time after which the lamp -The time after which the lamp ceases to operateceases to operate

-The time after which the light -The time after which the light

output is so reducedoutput is so reduced

Lamps - incandescentLamps - incandescent - discharge lamps- discharge lamps

INCANDESCENT INCANDESCENT TungstenTungsten

Tungsten halogenTungsten halogen

TUNGSTENTUNGSTEN Operate by heating a tungsten Operate by heating a tungsten

filament filament

Filled with an inert gasFilled with an inert gas

ADVADV Immediate full light outputImmediate full light output

Lamps operate in all positionLamps operate in all position

Easy to control the lampEasy to control the lamp

DIS ADVDIS ADV Short lifeShort life

Sensitive to vibrationSensitive to vibration

Not used for colour matchingNot used for colour matching

TUNGSTEN HALOGENTUNGSTEN HALOGEN Filament lampFilament lamp

Filled with halogen compound gasFilled with halogen compound gas

ADVADV Higher luminous efficacyHigher luminous efficacy

Lamp life longerLamp life longer

Small & compact ideal for optometric Small & compact ideal for optometric instrumentsinstruments

DIS ADVDIS ADV Surface of the bulb is liable to Surface of the bulb is liable to

deteriorate deteriorate

if touched with the fingersif touched with the fingers

DISCHARGE LAMPSDISCHARGE LAMPS Utilize the ionization of gas to produce Utilize the ionization of gas to produce

light light - fluorescent (low pressure - fluorescent (low pressure

mercury) mercury) lampslamps

-compact fluorescent lamps -compact fluorescent lamps -high pressure mercury lamps-high pressure mercury lamps -low pressure sodium lamps-low pressure sodium lamps -high pressure sodium lamps-high pressure sodium lamps -inductions lamps-inductions lamps

FLUORESCENT LAMPFLUORESCENT LAMP Known as tubular fluorescent lampKnown as tubular fluorescent lamp

Produces radiation in the visibleProduces radiation in the visible

COMPACT FLUORESCENT LAMPCOMPACT FLUORESCENT LAMP

Smaller versions of long distance Smaller versions of long distance tubetube

HIGH PRESSURE MERCURY HIGH PRESSURE MERCURY LAMPSLAMPS

Consists of quartz arc tubeConsists of quartz arc tube

Used in industrial & road lightiningUsed in industrial & road lightining

LOW PRESSURE SODIAM LAMPLOW PRESSURE SODIAM LAMP

Radiation emitted from these lamp is Radiation emitted from these lamp is monochromaticmonochromatic

Used for street lighteningUsed for street lightening

HIGH PRESSURE SODIUM LAMPHIGH PRESSURE SODIUM LAMP

Emit more continuous spectrumEmit more continuous spectrum

Have better colour propertiesHave better colour properties

Used in road lightning , sports hallUsed in road lightning , sports hall

INDUCTION LAMPSINDUCTION LAMPS New typeNew type

Known as eletrodeless lampKnown as eletrodeless lamp

ADV OF DISCHARGE LAMPSADV OF DISCHARGE LAMPS Lamp life longerLamp life longer

Excellent colour rendering propertiesExcellent colour rendering properties

DIS ADVDIS ADV FlickerFlicker

Stroboscopic effects Stroboscopic effects