LIGHT IS A SOURCE OF ENERGY THERE ARE TWO TYPE OF SOURCE OF LIGHT NATURAL SOURCE Eg : SUN ARTIFICIAL SOURCE Eg : LED

1. LIGHT
BY:
ABHINAV S (2ND YEARMBBS)
GMCTHIRUVALLUR, TAMILNADU

2. INTRODUCTION
• LIGHT IS A SOURCE OF ENERGY
• THERE ARE TWO TYPE OF SOURCE OF LIGHT
 NATURAL SOURCE
Eg : SUN
 ARTIFICIAL SOURCE
Eg : LED

3. REQUIREMENT FOR GOOD
LIGHTING
SUFFICIENT ILLUMINATION OF 15-20 FOOT CANDLES
UNIFORM DISTRIBUTION IN WORKING SPACE
ABSENCE OF GLARE
ABSENCE OF SHARP SHADOWS
STEADINESS OF SOURCE OF LIGHT
WHITE COLOUR OF THE LIGHT
CONTRAST SURROUNDINGS

4. MEASUREMENT OF LIGHT
• WHAT WE PERCIEVE AS LIGHT IS A NARROW WAVELENGHT
BAND OF ELECTROMAGNETIC RADIATION FROM ABOUT 380-
780 nm
• THE LUMINOUS INTENSITY OR POWER OF ARTIFICIAL LIGHT
IS MEASURED BY STANDARD ‘CANDLE ‘
• THE AMOUNT OF LIGHT GIVEN OFF BY THE BURNING OF
SPERMWAX CANDLE BURNING 120 GRAINS PER HOUR IS
CALLED ONE CANDLE POWER

5.  THERE ARE FOUR MEASURES OF IMPORTANCE
1: LUMINOUS INTENSITY-WHICH IS THE POWER OF THE LIGHT SOURCE
CONSIDER AS A POINT RADIATING ALL DIRECTION, MEASURED AS
CANDELA
2: LUMINOUS FLUX:FLOW OF LIGHT ,MEASURED IN LUMEN
3: ILLUMINATION OR ILLUMINANCE :AMOUNT OF LIGHT REACHING
THE SURFACE MEASURED IN LUX PER UNIT AREA
4: BRIGHTNESS OR LUMINANCE : AMOUNT OF LIGHT REFLECTED
FROM A SURFACE MEASURED IN LAMBERTS

7. MEASUREMENT OF
DAYLIGHT
• IT RELAYS ON THE FACTOR CALLED DAYLIGHT FACTOR SINCE
THE INTENSITY OF THE DAYLIGHT (DF) ILLUMINATION IS
LIKELY TO CHANGE FROM MOMENT TO MOMENT

8. NATURAL LIGHTING
IT IS DERIVED PARTLY FROM VISIBLE LIGHT AND PARTLY
FROM REFLECTION
IT DEPENDS UPON TIME OF THE DAY , SEASON , WEATHER
AND ATMOSPHERIC POLLUTION

9. SUGGESTION FOR IMPROVING DAYLIGHT
1:ORIENTATION:BUILDING SHOULD BE DIRECTED TOWARDS NORTH AND
SOUTH SO THAT THERE WILL BE UNIFORM LIGHTING FROM MORNING TO
EVENING
2:REMOVAL OF OBSTRUCTION:TO REMOVAL OF OBSTRUCTIVE ITEMS
EITHER WHOLLY OR PARTIALLY IS LIKELY TO GIVE MOST EFFECTIVE
IMPROVEMENT IN LIGHTING
3:WINDOWS:WINDOWS SHOULD BE PROPERLY PLANNED. A TALL NARROW
WINDOW GIVES GREATER PENETRATION OF LIGHT AND A BROAD
WINDOW GIVE GREATER DIFFUSION OF LIGHT
4:INTERIOR OF THE ROOMS: INSIDE THE ROOMS THE CEILING SHOULD BE
WHITE, THE UPPER PORTION OF THE WALL SHOULD BE LIGHT COLOUR
AND LOWER PORTION SHOULD BE SLIGHTLY DARK COLOURED

10. ARTIFICIAL LIGHTING
DAYLIGHT IS NOT AVAILABLE ALWAYS LIKE ON CLOUDY DAYS
etc.
SO ARTIFICIAL LIGHT IS SUPPLIMENT LIGHTING

11. FIVE SYSTEMS OF ARTIFICIAL LIGHTING
1. DIRECT LIGHTING :
 99-100 % OF LIGHT IS PROJECTED DIRECTLY TOWARDS WORKING AREA
 IT IS EFFICIENT,ECONOMICAL AND TENDS TO CAST SHARP SHADOWS
 IT SHOULD NOT FALL INTO EYES
2. SEMIDIRECT:-
 10-40% OF LIGHT IS PROJECTED UPWARDS SO THAT IT IS REFLECTED BACK ON
THE OBJECT BY THE CEILING

12. 3:INDIRECT
LIGHT DOES NOT STRIKE A SURFACE DIRECTLY BECAUSE 90-100% OF
LIGHT IS PROJECTED TOWARDS THE CEILING AND WALLS
4:SEMI-INDIRECT
60-90% OF LIGHT IS DIRECTED UPWARDS AND REST IS DOWNWARDS
5:DIRECT-INDIRECT
LIGHT IS DISTRIBUTED EQUALLY

13. METHODS OF ARTIFICIAL ILLUMINATION
FILAMENT LAMPS
• WIDELY USED
• ELECTRIC CURRENT HEATS UP THE TUNGSTEN FILAMENT AND LIGHT
EMITTED DEPENDS UPON THE TEMPERATURE
FLUORESCENT
• FLUORESCENT LAMB ARE ECONOMICAL IN USE OF ELECTRIC CURRENT
• THEY ARE COOL AND EFFICIENT
• THE LAMP CONSIST OF A GLASS TUBE FILLED WITH MERCURY VAPOUR AND
ELECTRODE FILLED IN EACH END
• INSIDE TUBE COATED WITH FLUORESCENT CHEMICAL WHICH ABSORB ALL UV
RADIATION AND REMIT RADIATION IN VISIBLE RANGE

14. LIGHTING STANDARDS
• EYE RESPOND TO RANGE OF ILLUMINATION RANGING FROM 0.1 Lux (FULL
MOONLIGHT) TO 10000 Lux (BRIGHT SUNSHINE)
• THERE IS CONFUSION ABOUT STANDARD BECAUSE OF ADAPTIBILITY OF EYE
• VISUAL EFFICIENCY INCREASE WITH INCREASE IN ILLUMINATION
• A USEFUL RULE OF THUMB IS THAT THE ILLUMINATION LEVEL SHOULD BE 30
TIMES HIGHER THAN LEVEL AT WHICH TASK CAN BE DONE
• FOR PRACTICAL SITUATION AND VARIOUS ACTIVITIES THE FOLLOWING
VALUES HAVE SUGGESTED BY ILLUMINATING ENGINEERING SOCIETY

16. BIOLOGICAL EFFECT OF LIGHT
• SOME THEORIES ABOUT IT IS THAT DAYLIGHT COULD CAUSE IN
VITRO DEGRADATION OF BILIRUBIN IS NOW BEING USED AS A
THERAPEUTIC MEASURE IN PREMATURE INFANT WITH
HYPERBILIRUBINAEMIA
• OTHER BIOLOGICAL EFFECT ARE EFFECT OF BIOLOGICAL
RHYTHM OF THE BODY TEMPERATURE, PHYSICAL ACTIVITY , THE
STIMULATION OF MELANIN SYNTHESIS , THE ACTIVATION OF
PRECURSER OF VITAMIN D ,ADRENOCORTICAL SECRETION AND
FOOD CONSUMPTION

17. REFERENCE