Illumination Basic and Scheme

Topics
1. Introduction
2. Nature of light
3. Lighting schemes
4. Terms used in illumination
5. Electrical methods of producing light
6. Arc lamps
7. Filament lamps
8. Gaseous discharge lamps
7. Sodium vapour lamp
8. Mercury vapour lamp
9. Fluorescent tube
10. Neon lamp
11. Halogen lamp
12. Compact fluorescent lamp
Introduction
 As we know that almost all human activities depends on light.
Sun is a prime natural source of light but artificial lighting
plays almost main role in our daily life. These artificial lights
are produced by mechanical lamps and electrical lamps.
 But due to poor performance the mechanical light are
totally replaced by electrical lights. The electrical lighting
are mainly used for decorative purpose, advertising, traffic
control,medical field and street lighting etc.
Electrical Lighting
Electrical lighting has following advantages :
1. Cleanliness
2. Easy to control
3. Economical
4. Easy to handle
5. Better reliability
6. Suitable for almost all purposes etc.
TERMS USED IN
ILLUMINATION
1.Light
2. Luminous Flux
3. Luminous Intensity
4. Illumination
LIGHT
 Light is a form of electromagnetic energy, that part of
radiant energy from a hot body which produced the visual
sensation on human eye is called light.
 Light can be of different colours, which depend on the
wavelength of radiation causing it.
LUMINOUS FLUX
 To measure light, it is necessary to measure its flux (rate of
flow)
 The total quantity of radiant energy per second responsible
for visual sensation from a luminous body is called
Luminous Flux.
Or
Rate of flow of radiant energy
 Measured in lumens.
LUMINOUS INTENSITY
 Intensity of emission of luminous flux in that direction
is the luminous intensity.
 It is denoted by I and its unit is candela or candle power
(CP) .
 Luminous intensity of source in a particular direction,
I=φ/ω
ILLUMINATION
 When light falls on a surface, it becomes visible, the
phenomenon is called as illumination.
 It is defined as luminous flux falling on a surface per
unit area.
 It is denoted by E and measured in lumen per square
meter or meter‐ candle.
E = Ф / A lux
Lighting Schemes
 Lighting schemes are classified according to the location,

requirement and purpose etc. are as under :
1. Direct lighting
2. Indirect lighting
3. Semi direct lighting
4. Semi indirect lighting
5. General lighting
Direct Lighting
 As is clear from the name, in this system almost 90 to 95
% light falls directly on the object or the surface.
 The light is made to fall upon the surface with the help of
deep reflectors.
 Such type of lighting scheme is most used in industries
and commercial lighting.
 Although this scheme is most efficient but it is liable to
cause glare and shadows.
Indirect Lighting
 In this system, the light does not fall directly on the
surface but more than 90 % of light is directed
upwards by using diffusing reflectors.
 Here the ceiling acts as a source of light and this light is
uniformly distributed over the surface and glare is
reduced to minimum.
 It provides shadow less illumination which is useful for
drawing offices.
 It is also used for decoration purposes in cinema halls,
hotels etc.
Semi direct Lighting
 This is also an efficient system of lighting and chances of
glare are also reduced.
 Here transparent type shades are used through which
about 60 % light is directed downward and 40 % is
directed upward.
 This also provides a uniform distribution of light and is
best suited for room with high ceilings.
Semi indirect Lighting
 In this system about 60 to 90 % of total light is thrown

upward to the ceiling for diffused reflection and the rest
reaches the working plane directly.
 A very small amount of light is absorbed by the bowl.
 It is mainly used for interior decoration.
General Lighting
 This system employs such type of

luminaries, shades and reflectors which
give equal illumination in all the
directions.
LAMPS
FILAMENT OR
INCANDESCENT LAMP
Properties of Metal for Filament
1. High melting point : so that it can be operated at high

temperature.
2. High specific resistance : so that it produces more heat.
3. Low temperature coefficient : so that filament
resistance may not change at operating temperature.
4. Low vapour pressure ; so that it may not vaporize
5. High ductile : so that it may withstand mechanical
vibrations
SODIUM VAPOUR LAMP
Life of such lamps ends when:-
1. Filament breaks or burns out

2. The cathode stops to emit electrons
3. When sodium particles may concentrate
to one side of the tube
MERCURY VAPOUR LAMP
FLUORESCENT TUBE
NEON LAMP
HALOGEN LAMP
COMPACT FLUORECENT LAMP
Design of Indoor Light Scheme
While designing a good lighting schemes, the following points

must be kept in mind :
1. It should provide adequate illumination.
2. It should provides uniformly distributed light all over
working plane.
3. It should avoid glare and shadows as far as possible.
4. It should provide light of suitable colours.
Factors required for Light Scheme
The following factors are required to be considered while
designing the lighting scheme :
1. Illumination level
2. Quality of light
3. Co efficient of utilization
4. Depreciation factor
5. Space height ratio
Illumination Level
 Type of work recommended illumination
level
 Offices 100‐400 lumens/ meter square
 Schools 250‐400 lumens/ meter square
 Industry 1000 lumens/ meter square
 Shops 250‐500 lumens/ meter square
 Hotels 80‐100 lumens/ meter square
 Hospitals 250‐3500 lumens/ meter square
Quality of Light
 This means that the illumination should not be harmful
to the viewers.
 It should be glare free, shadow less and contrast free.

Hard and long shadows can be avoided by using a
large number of lamps and adjusting the mounting
height.
Co – efficient of Utilization
 Utilization factor =
lumens reaching at the working place/total lumens
emitted by the source
 Usually it varies from 0.5 to 0.8.

Depreciation Factor
 The total flux emitted by the source and its fitting may be
reduced due to deposition of dust upon the surfaces.
 Similarly quantity of light reflected from the ceiling and

walls also decreases with the passage of time. This is
called as depreciation factor.
 Usually it varies from 1.3 to 1.6

Space Height Ratio
 The ratio of space (horizontal distance ) between the

two adjacent lamps to the vertical height of the lamps
above the working plane is called space height ratio.

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Topics

 Lighting schemes are classified according to the location,

 In this system about 60 to 90 % of total light is thrown

 This system employs such type of

1. High melting point : so that it can be operated at high

1. Filament breaks or burns out

While designing a good lighting schemes, the following points

 It should be glare free, shadow less and contrast free.

 Usually it varies from 0.5 to 0.8.

 Similarly quantity of light reflected from the ceiling and

 Usually it varies from 1.3 to 1.6

 The ratio of space (horizontal distance ) between the

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