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Illumination Engineering

a branch of electrical engineering, deals with the science and art of producing artificial light.

Illumination Engineering

It focuses on the principles and techniques for designing and implementing lighting systems in various settings

Light

is an electromagnetic wave exhibiting both wave and particle behavior.

Light

very small part of the electromagnetic spectrum, sandwiched between ultraviolet and infrared radiation.

light

visible portion of the electromagnetic spectrum extends from about 380 to about 780 nanometers (nm)

light

radiant energy that is capable of exciting the retina and producing a visual sensation

electromagnetic (EM) spectrum

is the entire range of electromagnetic radiation, classified according To wavelength or frequency.

light

radiant energy from a hot body that produces the visual sensation upon the human eye.

light

It is expressed in lumen hours and it analogous to watthours,

luminous flux

It is defined as the energy in the form of light waves radiated per second from a luminous body.

Radiant efficiency

When an electric current is passed through a conductor, some heat is produced to I2R loss, which increases its temperature of the conductor.

Radiant efficiency

is defined as the ratio of energy radiated in the form of light, produces sensation of vision to the total energy radiated out by the luminous body’.

Rectilinear propagation

Light travels in straight lines.

Reflection

Light striking a smooth surface turns back into the original medium.

Refraction

Light bends when entering a transparent medium.

plane angle

is the angle subtended at a point in a plane by two converging lines.

Solid angle

The angle subtended at a point in space by an area, i.e., the angle enclosed in the volume formed by numerous lines lying on the surface and meeting at the point.

solid angle

is measured in steradian.

Luminous intensity

in a given direction is defined as the luminous flux emitted by the source per unit solid angle.

Lumen

It is the unit of luminous flux.

lumen

It is defined as the luminous flux emitted by a source of one candle power per unit solid angle in all directions.

Candle power

of a source is defined as the total luminous flux lines emitted by that source in a unit solid angle.

Illumination

is defined as the luminous flux received by the surface per unit area.

Lux or meter candle

It is defined as the illumination of the inside of a sphere of radius 1 m and a source of 1 CP is fitted at the center of sphere.

Foot candle

It is the unit of illumination and is defined as the illumination of the inside of a sphere of radius 1 foot,

Brightness

of any surface is defined as the luminous intensity per unit surface area of the projected surface in the given direction.

MHCP

is defined as the mean of the candle power of source in all directions in horizontal plane.

MSCP

is defined as the mean of the candle power of source in all directions in all planes.

MHSCP

is defined as the mean of the candle power of source in all directions above or below the horizontal plane.

Reduction factor

of the source of light is defined as the ratio of its mean spherical candle power to its mean horizontal candle power.

Lamp efficiency

It is defined as the ratio of the total luminous flux emitting from the source to its electrical power input in watts.

Specific consumption

It is defined as the ratio of electric power input to its average candle power.

Space to height ratio

It is defined as ratio of horizontal distance between adjacent lamps to the height of their Mountings.

Coefficient of utilization or utilization factor

It is defined as the ratio of total number of lumens reaching the working plane to the Total number of lumens emitting from source.

Maintenance factor

It is defined as the ratio of illumination under normal working conditions to the illumination when everything is clean.

Depreciation factor

It is defined as the ratio of initial illumination to the ultimate maintained illumination on the working plane. Its values is always more than 1.

Lighting design

process of selecting the right kind of luminaires to produce light of the required quantity and quality at the right location.

POINT BY POINT METHOD

This method permits the determination of illumination level due to one or more sources upon a specific point within an area,

Inverse square law

This law states that “the illumination of a surface is inversely proportional to the square of distance between the surface and a point source”.

Lambert's cosine law.

This law states that ‘illumination, E at any point on a surface is directly proportional to the cosine of the angle between the normal at that point and the line of flux’.

Incandescent Lamp

produce light by electrically heating high

argon and nitrogen

A filling of inert gas, such as ___, retards evaporation of the filament, thus allowing higher filament temperature and, hence higher efficiencies with less sacrifice of life. Bulbs under 40 watts are generally evacuated.

standard

what is A in incandescent lamp

pear shaped

what is PS in incandescent lamp

Reflector

what is R in incandescent lamp

parabolic aluminized reflector

stands for "PAR"

Tungsten Halogen Lamp

Also known as quartz

iodine or bromine

tungsten halogen Lamps contain a halogen gas such as___, operate at high temperatures, and have a smaller envelope.

quartz

The outer envelope of tungsten halogen lamp is made of __ to withstand the very high temperature.

Krypton

filled lamps

Krypton filled lamps

replace the existing 40

Ellipsoidal reflector lamps

replace "A" or "R" lamps

Ellipsoidal reflector lamps

When a point source of light is placed at the first focal point of an elliptical reflector, all reflected lights emerge through the second focal point.

Ellipsoidal reflector lamps & Krypton filled lamps

Energy saving incandescent lamps

Fluorescent lamps

produce light by creating an arc between two electrodes in an atmosphere of low pressure mercury vapor and some inert gas in a glass tube.

Fluorescent lamps

requires a ballast to strike the electric arc in the tube initially and to maintain that arc.

Fluorescent lamps

twice that of incandescent.

Cool white, warm white or daylight

what color is on fluorescent lamp

Compact fluorescent lamps (CFL)

effective alternative to traditional incandescent lamps.

Compact fluorescent lamps (CFL)

same light output as incandescent while consuming only 20% of energy.

mercury vapour, metal halide,High pressure sodium.

High intensity discharge lamps (HID)

High intensity discharge lamps (HID)

produce light by establishing an arc between electrodes, enclosed in opposite ends of sealed translucent or transparent arc tubes.

Mercury Vapor

Arc tube enclosed in outer bulb that is filled nitrogen and inert gas in

metal halide

Arc tube enclosed in outer bulb that is filled vacuum or nitrogen in

high pressure sodium

Arc tube enclosed in outer bulb that is filled Vacuum or xenon in

true

If power is switched off, the arc tube must cool before it can be restruck again and light produced.

Mercury vapour lamps

The outer tube is filled with nitrogen and encloses the inner arc tube which contains high purity mercury and argon gas.

true

As the circuit is energized the starting voltage is provided across the starting electrodes and the adjacent main electrode to create an argon arc. This increases the heat and vaporized mercury.

Metal Halide

similar to MV lamps in operating, principle.

Metal Halide

ideally suitable for high ceiling areas where a lot of light with good color is required.

High pressure sodium vapour lamp (HPS)

The arc tube is made of ceramic translucent aluminum oxide, which can withstand temperatures as high as 1300 °C.

High pressure sodium vapour lamp (HPS)

color for golden white color

Direct Lighting

in the form of lighting, the light from the source falls directly on the object or the surface to be illuminated

Direct Lighting

The division is usually 60% downwards. With the help of shades and globes and reflectors

Direct lighting,

though most efficient, is liable to cause glare and hard shadows.

Indirect Lighting

In this form of lighting, light does not reach the surface directly from the source but indirectly by diffuse reflection

Indirect Lighting

The division is usually 80% upwards and 10% downwards. The lamps are either placed behind a cornice or in suspended opaque bowls.

Indirect Lighting

maximum light is thrown upwards on the ceiling from which it is distributed all over the room by diffuse reflection.

indirect lighting

is that it provides shadowless illumination which is very useful for drawing offices, composing rooms and in workshops especially where large machines and other obstructions would cast troublesome shadows if direct lighting were used.

Semi direct System

This system utilizes luminaries which send most of the light downwards directly on the working plane but a considerable amount reaches the ceilings and walls also

semi direct system

The division is usually 30% upwards and 45% downwards.

semi direct system

Such a system is best suited to rooms with high ceilings where a high level of uniformly distributed illumination is desirable.

true

Glare in such units is avoided by using diffusing globes which not only improve the brightness towards the eye level but improve the efficiency of the system with reference to the working plane.

Semi indirect Lighting

In this system which is, in fact, a compromise between the first two systems, the light is partly received by diffuse reflection and partly direct from the source

Semi indirect Lighting

The division is usually 75% upwards and 10% downwards. Such a system, therefore, eliminates the objections of indirect lighting mentioned above.

semi indirect lighting

Instead of using opaque bowls with reflectors, translucent bowls without reflector are used.

true

the semi indirect lighting Most of the light is, as before, directed upwards to the ceiling for diffuse reflection and the rest reaches the working plane directly except for some absorption by the bowl.

General Diffusing System

In this system, luminaries are employed which have almost equal light distribution downwards and upwards

AVERAGE LUMEN METHOD

much more simplified way of calculating an average uniform illuminance level on a plane in interiors.

AVERAGE LUMEN METHOD

takes into account the effects of surface reflectance and offers a simplified and accurate method of quantity evaluation for interiors.

AVERAGE LUMEN METHOD

developed from the basic definition of lux, which states that one lux is the illuminance on a surface of one square metre having a light flux of one lumen.

TRUE

Initial illuminance level In reality, all the luminous flux generated by the lamps will not fall on the work plane. number of factors like room geometry, surface reflectance and luminaire height, will affect the total number of lumens reaching the work plan

Maintained illuminance level

The luminaire, lamp and even the surface will accumulate dust over a period of time and the lamp lumen output will depreciate with time

LUMEN

Unit of luminous flux.

Luminous Flux

The total quantity of radiant energy per second responsible for visual sensation from a luminous body is called

Coefficient of utilization (η)

It is the ratio of the lumens actually received by a particular surface to the total lumens emitted by a luminous source.

Ceiling reflectance

most significant effect on CU values with luminaires that produce light upwards, indirect and direct indirect types of luminaires fall in this category.

Wall reflectance

has a significant effect on CU values of almost all luminaires, and particularly for luminaires with wide spread distribution.

Floor reflectance

has least effect on CU values, since most tasks are located above work plane.

LIGHT LOSS FACTOR (ρ)

This factor allows for the fact that effective candle power of all lamps or luminous sources deteriorates owing to blackening and/or accumulation of dust or dirt on the globes and reflectors etc.