The document provides an extensive overview of lighting, covering topics such as energy conversion to light, the human eye and vision, and various light sources. It details quantities and measurements related to light, the electromagnetic spectrum, and the physics of light generation, while also emphasizing the significance of proper lighting for human activities. Furthermore, it discusses artificial illumination systems and their components, types of light sources, and the impact of lighting on visual perception and comfort.

1. Chapter 1 Introduction
Topics to be covered 8 Hours
Radiant energy and visible spectrum, energy conversion to light, colour , eye and vision; different
entities of illuminating systems.
Light sources: Daylight, incandescent, electric discharge, fluorescent, arc lamps and lasers; Energy
efficient lamps; Luminaries, wiring, switching and control circuits. Importance of Lighting in Human
Life: Optical systems of human eye. Dependence of human activities on light, performance
characteristics of human visual system, External factors of vision-visual acuity, contrast, sensitivity,
time illuminance, colour, visual perception, optical radiation hazards, Good and bad effects of lighting
and perfect level of illumination, Artificial lighting as substitute to natural light, Ability to control
natural light, Production of light, physics of generation of light, Properties of light, Quantification and
Measurement of Light.
1.1 Basic Concepts:

2.  Radiation: Is the emission or transfer of energy in the form of electromagnetic waves.
 Light: It is defined as the radiation energy from a hot body which produces the visual
sensation upon the human eye. It is usually denoted by Q, expressed in lumen-hours and is
analogous to watt-hour.
The band of wave length that corresponds to visible light lies between 380 nm and 760 nm
(1 nm = 10-9
m)
Or
Electromagnetic radiation within the visible spectrum that enables us to perceive our
surroundings.
 Eye sensitivity: The human eye is sensitive to different wave lengths (color) with varied
efficiency. It is different for scotopic and photopic vision.
 Luminous Flux (Φ): The total amount of visible light (radiant flux) emitted by a light
source (lamp), measured in lumens (lm).
 Illuminance (E) : Quantity of light (lumens) incident on a surface per unit area (m2). The
unit is 'lux' (lumen/ m2).
or
The amount of light falling on a surface, measured in lux (lx), where 1 lux is equivalent to
1 lumen per square meter.
 Luminance (L): The amount of light or Intensities (candela) of light reflected back from
a surface per unit area (m2) in a particular direction. The unit is candelas per square
meter (cd/m²).
 Luminous intensity: Luminous intensity in any given direction is the luminous flux
emitted by the source per unit solid angle, measured in the direction in which the intensity
is required. It is denoted by symbol I and is measured in candela (cd) or lumens/steradian.
 Luminous efficacy: Quantity of light (lumen) emitted for each unit of electrical power
(watt) consumed. The unit is 'lumen/watt' (lm/W).
 Illumination: When the light falls upon any surface, the phenomenon is called the
illumination. It is defined as the number of lumens, falling on the surface, per unit area. It
is denoted by symbol E and is measured in lumens per square meter or meter-candle or lux.
 Reflectance (ρ): The ratio of light reflected by a surface to the light incident on it.
 Visual Comfort: Ensuring lighting that does not cause discomfort or strain to the human
eye, providing a pleasant visual experience.

3.  Color rendering: Expression for the effect of an illuminant on the colour of an object in
conscious comparison with their color as seen under a reference illuminant (daylight).
 Color rendering index (Ra): Measure of the degree to which the colors of objects
illuminated by a source conform to that when illuminated by a reference source
(daylight).
 Color temperature: Temperature of the black body that emits radiation identical as the
radiation under study. The unit is °K
 Black body: A thermal radiator that absorbs all incident radiations. The emitted radiation
corresponds to specific color appearances at a given temperature.
 Coefficient of utilization : It is the ratio of the lumens reaching the working (C.O.U.)
plane to the total lumens produced. It is also called "Utilisation Factor". C.O.U. depends
on, light distribution of the luminaire; light output ratio of the luminaire; reflectance of
the ceiling, walls & working plane; room index and arrangement of the luminaires in the
room. C.O.U. is based on new, clean equipment and in practice a maintenance factor is
introduced to convert initial to in- service illumination.
 Maintenance Factor : The maintenance factors is the ratio of the lumens produced by
the system while in service to the lumens produced by system when newly installed.
 Room Index (K) : The room index K is a function of the room luminaire and is given as
follows
K =
L x W
𝐻𝑚𝑋(𝐿+𝑊)
L = Length of room
W = Width of Room
Hm = Mounting height of the luminaires
 Uniformity Ratio (UR): It is the ratio of minimum lux in a given plane to the average
lux.
 Lamp lumen Depreciation (LLD) : The lumen output of all lamps decrease with use,
but the rate of decrease varies widely between lamp types and between manufactures.
Lighting calculation must take into account specific depreciation in lumen output of the
light source.
 Glare: A condition which leads to discomfort or a reduction in the ability to see objects,
or both, due to distribution of intensities/ extreme contrasts in the field of vision.

4.  Light output ratio (LOR): The ratio of the total flux from the luminaire, to the sum of
the luminous fluxes of lamps.
1.2 Radiant energy:
 Radiant energy refers to the energy carried by electromagnetic waves, including light,
which is a form of electromagnetic radiation.
 It is the energy that is transmitted through space via electromagnetic waves without the
need for a medium (like air or water) to propagate.
 Radiant energy includes a wide range of electromagnetic wavelengths, from radio waves
to gamma rays
1.2.1. Electromagnetic Spectrum:
• The electromagnetic spectrum categorizes electromagnetic waves based on their
wavelengths or frequencies.
• It encompasses a wide range of wavelengths, from the longest radio waves to the shortest
gamma rays.
• The spectrum includes radio waves, microwaves, infrared radiation, visible light,
ultraviolet radiation, X-rays, and gamma rays.
Fig.1 shows how sunlight splits into various color bands spread over violet to red often termed
vibgyor. Energy is spread over this spectrum from the sunlight. Fig.1 shows how sunlight splits
into various color bands spread over violet to red often termed vibgyor. Fig. 2 shows the relative
energy content of the solar radiation. While Fig. 3 shows the response of human eye to the solar
radiation, which is maxima at about 550nm. (Corresponding to yellow green color).
1.2.3 Relative Energy:

5. 1.2.4. Relative Luminosity:
This being the scenario of natural light, artificial sources are made to produce radiation close to
this. Artificial sources employed are Incandescent lamps which depend on temperature of the
filaments giving a continuous spectrum and gas or discharge lamps giving a discontinuous – Line
spectrum / Band spectrum.
1.2.5. Visible Spectrum:
• The visible spectrum is a specific portion of the electromagnetic spectrum that is visible to the
human eye.
• It covers the range of wavelengths roughly from 380 nanometers (violet) to 750 nanometers
(red).
• Different colors in the visible spectrum correspond to different wavelengths of light.
Colors of the Visible Spectrum:
• Red: Longest wavelength in the visible spectrum, around 620-750 nm.
• Orange: Wavelengths around 590-620 nm.
• Yellow: Wavelengths around 570-590 nm.
• Green: Wavelengths around 495-570 nm.
• Blue: Wavelengths around 450-495 nm.

6. • Indigo: Wavelengths around 420-450 nm.
• Violet: Shortest wavelength in the visible spectrum, around 380-420 nm.
1.2.6. Perception of Color:
 Color is a perceptual property of light determined by its wavelength.
 Our perception of color is based on the wavelengths of light that are either absorbed or
reflected by objects.
 An object appears a particular color because they absorb certain wavelengths and reflect
others.
 The human eye contains specialized cells called cones that are sensitive to different parts
of the visible spectrum, allowing us to perceive a wide range of colors.
 The primary colors of light are red, green, and blue (RGB), and mixing them creates other
colors.
1.2.7. Applications of Visible Light:
Visible light has various practical applications, including:
• Illumination: Lighting for various environments, indoors and outdoors.
• Communication: Optical fibers transmit data using light signals.
• Photography and Imaging: Capturing visual information using cameras and other imaging
devices.
• Display Technologies: LCD, OLED, and LED displays use visible light to create images.
• Spectroscopy: Analyzing the composition of materials based on their interactions with light.
1.3. Energy Conversion to Light:
Light is generated by converting energy from various sources:
1. Incandescence: Thermo luminescence is by definition is a radiation emitted at high
temperature. The sources employing this process are Incandescent Lamp, Gas Lamp, (flames and
in oil Lamps and wax candles). They lead to a continuous spectrum of radiation.
2. Luminescence –Electro luminescence by definition is a Chemical or Electrical Action on gases
or vapour radiation. Here color of radiation depends on the material employed. Usually this process
leads to Line or Band Spectrum.

7. 3. Fluorescence-Fluorescence is a process in which radiation is absorbed at one wavelength and
radiated at another wavelength Eg: UV impinging on Uranium – Fluorescent oils. This re radiation
makes the light radiated visible.
4. Phosphorescence- Phosphorescence is a process when energy is absorbed at some time and
radiated later as glow. Examples of this process are Luminous paints that contain calcium sulfide
that lead to Phosphorescence. They produce light Radiation after exposure to light. In practice
good efficient lighting is obtained by combining Luminescence and Fluorescence.
Fluorescent lamp is Luminescent source of low luminous value activating Fluorescent surfaces
which lead to visible radiation. Here intensity depends on gas or vapor involved and phosphor
material. However, the temperature of the material play a role in radiation.
1.4. Eye and Vision:
1.4.1. The Eye:
The eye is a complex organ responsible for detecting and processing visual information from the
surrounding environment. It works in conjunction with the brain to create the sensation of vision.
• The eye's main components include the cornea, lens, iris, retina, and photoreceptor cells (rod
and cones).
• Rods are sensitive to low light and contribute to night vision, while cones perceive color in
brighter light.
• The brain processes signals from these cells to create visual perceptions.
Fig. 4 shows the structure of eye
Fig. 4: Structure of the Eye
Cornea: The transparent outermost layer of the eye that helps focus incoming light.

8. Iris: The colored part of the eye that controls the size of the pupil and regulates the amount of light
entering the eye by expanding /contracting.
Pupil: The dark circular opening in the center of the iris that lets light into the eye.
Lens: A flexible, clear structure that focuses light onto the retina. Lens that focuses light under the
control of ciliary muscles forms image on to the retina. The lens is crystalline in nature.
Retina: Lastly there is a screen like structure called retina that is holding a lot of - optic nerves –
that communicate with the brain. The innermost layer of the eye containing photoreceptor cells
(rods and cones) that convert light into neural signals. The central region has the greatest sensitivity
and is called Fovea.
Fovea is the most acute spot of vision where fine details are formed. Rest of the retina is
responsible for orientation. The eye communicates through optic nerves located on the retina.
Optic Nerve: The bundle of nerve fibers that carries visual information from the retina to the brain.
Types of Photoreceptor Cells:
Rods: Responsible for low-light vision and peripheral vision. They don't perceive color.
Cones: Responsible for color vision and visual acuity. There are three types of cones, each
sensitive to different wavelengths of light (red, green, and blue).
1.4.2. Vision:
Vision is of two types:
Photopic vision : involving cone cells and is used for discrimination of fine details for critical
observation. They are densely packed and transmits sharp images. The cone cells have low
sensitivity below 0.01 ft lamberts and cease to function < 0.001 ft lamberts. It must be mentioned
that by definition 1 lambert is
1
𝜋
candles /m2
and 1 ft lambert is
1
𝜋
candles / ft2
.
Scotopic vision: involving Rods takes over when brightness < 0.01 ft lambert. This vision has no
color discrimination ability. Most images have gray appearance and are viewed as silhouettes
lacking sharp details.
Eyes have good ability to change from one to other. This shift in Luminosity and ability of eye
to adjust is known as Purkinjee effect. Upon increase of intensity of illumination by a decrease
in Pupil size producing clearer images with greater and fine details. Pupil diameter varies in the
range of 1.2 – 2 mm. Eyes are error free and accommodate very well. So eye functions under

9. varying illumination levels by a change in pupil size together with change in Retinal Nerve
System (i.e. cones/ rods) as shown in Table II.
Table II Pupil size Vs Light received
Pupil Size or
Opening
Light
Received
Large
Small
Dim Light
High
Illumination
Table III shows the relationship of Eye opening to lens size, distance of object & color of focus
Pupil Opening Lens Shape Object Focus
Large
Small
Flattest
Convex
Distant
Near
Red
Blue
Vision Process:
• Light enters the eye through the cornea and pupil.
• The lens adjusts its shape to focus the incoming light onto the retina.
• Photoreceptor cells in the retina (rods and cones) convert light into electrical signals.
• These signals are sent through the optic nerve to the brain's visual cortex for processing.
• The brain interprets these signals to create the perception of a visual scene.
Eye Resembles – a Camera in general structure and action.
How Good lighting impacts on visibilty?
 Prevention of defective vision
 Optimization of Existing Resources
 Improving conditions of visibility.

10. Visibility depends on:
 Size/Details of the objects
 Level/Quality of Illumination
 Contrast/color
 Available time
 Efficacy of individual
 One’s eye defects
 Optical and Fatigue
 Distractions
Causes for Fatigue:
 Rotating surface
 Focusing on the source of glare
 Reading double impression
 After a day’s work pupil is dilated
A night rests offsets fatigue due to a day’s work
Eye defects are caused due
 Ageing
 Use
 Abuse
Functioning of the eye may be assessed by the Visual Acuity. Visual Acuity refers to the sharpness
and clarity of vision. It is dependent on the optical and nueral factors, i.e ,
1. The sharpness of the retinal focus within the eye.
2. The health and functioning of the retina.
3. The sensitivity of the interpretative area of the brain.
Acuity is the ability to distinguish details depending upon:
• Brightness of the object
• Characteristics of light enteringthe eye
• Contrast details.
Performance Characteristics of the Human Visual System:
• Visual acuity: Sharpness of vision, influenced by the ability to distinguish small details.
• Contrast sensitivity: Perception of contrasts between light and dark areas.
• Color vision: Ability to perceive colors accurately under different lighting conditions.

11. External Factors of Vision:
• Visual acuity, contrast, sensitivity, time illuminance, color, and visual perception are
influenced by factors like age, health, and lighting conditions.
1.5. Illuminating Systems:
Illuminating systems are designed to provide artificial lighting in various applications.
1.5.1. Different entities of illuminating systems include:
• Light Sources: Devices that emit light, like incandescent bulbs, fluorescent tubes, LEDs,
and lasers.
• Optics: Lenses, reflectors, and diffusers shape and direct light.
• Ballasts and Drivers: Regulate current for specific light sources (e.g., fluorescent
ballasts, LED drivers).
• Controls: Dimmers, timers, and sensors manage lighting levels and energy consumption.
• Fixtures: Housing for light sources, optics, and other components.
1.5.2. Types of Illuminating Systems:
• Incandescent Lighting: Produces light by heating a filament until it glows; inefficient due
to heat loss.
• Fluorescent Lighting: Excites phosphors with ultraviolet light emitted by mercury vapor,
producing visible light.
• LED Lighting: Light-emitting diodes emit light when current passes through a
semiconductor; energy-efficient and long-lasting.
• HID Lighting: High-intensity discharge lamps produce light through an electric arc
between electrodes (e.g., metal halide lamps).
• Natural Lighting: Utilizes daylight through windows, skylights, and light shelves; reduces
energy consumption.
1.6. Light Sources:
1.6.1. Types and Characteristics
Light sources are essential components of illuminating systems, providing various types of
lighting for different applications. Here are some common types of light sources, along with
their characteristics:

12. 1. Daylight:
• Source: Natural sunlight.
• Characteristics: Full spectrum of visible light; changes in intensity and color temperature
throughout the day; provides excellent color rendering.
• Applications: Daylighting in buildings, natural illumination for photography and art.
2. Incandescent Lamps:
• Source: Tungsten filament heated until it emits visible light.
• Characteristics: Warm color temperature (reddish-yellow), continuous spectrum;
inefficient due to heat production.
• Applications: General lighting in homes, decorative lighting.
3. Electric Discharge Lamps:
• Source: Electrically charged gas or vapor.
• Characteristics: High intensity, relatively efficient; various types based on the gas or
vapor used.
• Applications: Street lighting, industrial spaces, stadiums.
4. Fluorescent Lamps:
• Source: Mercury vapor emits ultraviolet light, which excites phosphors on the lamp's inner
surface to produce visible light.
• Characteristics: Higher efficiency than incandescent; relatively cool color temperature;
used with ballasts.
• Applications: Office lighting, commercial spaces, schools.
5. Arc Lamps:
• Source: Electric arc between two electrodes.
• Characteristics: Intense and directional light; high color temperature.
• Applications: Movie projectors, theatrical lighting, stage performances.
6. Lasers (Light Amplification by Stimulated Emission of Radiation):
• Source: Amplified light through stimulated emission; coherent and monochromatic.
• Characteristics: Narrow, focused beam; precise and high-intensity light; used in
scientific, medical, and industrial applications.
• Applications: Laser pointers, medical surgeries, cutting and welding in industry.

13. 1.6.2. Considerations for Choosing Light Sources:
• Energy Efficiency: LED and fluorescent lamps are more energy-efficient compared to
incandescent and some discharge lamps.
• Color Temperature: Different sources have different color temperatures, affecting the
mood and appearance of the lit space.
• Color Rendering: Some sources provide better color rendering than others, affecting how
accurately colors are perceived.
• Luminous Efficacy: Measure of how much visible light a source produces per unit of
energy consumed; higher values are more efficient.
• Longevity: LED and fluorescent lamps tend to have longer lifespans compared to
incandescent lamps.
1.7. Energy-Efficient Lamps
Energy-efficient lamps are lighting solutions designed to provide illumination while
minimizing energy consumption and reducing environmental impact. They have gained
popularity due to their ability to save energy and lower electricity bills. Here are some of the
most common types of energy-efficient lamps:
1. Compact Fluorescent Lamps (CFLs):
• Working Principle: CFLs use a gas-filled tube and phosphor coating to produce light
when excited by an electric current.
• Advantages:
• More energy-efficient than incandescent lamps.
• Last longer, typically around 8,000 to 10,000 hours.
• Available in various color temperatures and styles.
• Considerations:
• Initial cost may be higher than incandescent lamps.
• Some CFLs require a short warm-up time to reach full brightness.
• Contains a small amount of mercury, requiring proper disposal.

14. 2. Light-Emitting Diodes (LEDs):
Working Principle: LEDs emit light when current passes through a semiconductor material.
Advantages:
• Highly energy-efficient with lower power consumption.
• Long lifespan, often exceeding 25,000 hours or more.
• Instantaneous full brightness without warm-up time.
• Wide range of color temperatures and designs.
• Resistant to vibration and impact.
• Can be dimmed and controlled easily.
Considerations:
• Initial cost is higher than traditional lamps, but costs have been decreasing.
• Quality varies among brands, affecting performance and lifespan.
• LEDs may experience color shift over time in some cases.
3. Halogen Incandescent Lamps:
Working Principle: Halogen lamps are a type of incandescent lamp that uses halogen gas to
extend filament life.
Advantages:
• Slightly more energy-efficient and longer-lasting compared to traditional incandescent
lamps.
• Produces high-quality, white light.
• Dimmable and instant-on.
Considerations:
• Still less energy-efficient compared to CFLs and LEDs.
• Emit a significant amount of heat.
4. Energy-Efficient Incandescent Lamps:
Working Principle: Modified incandescent lamps designed to be more energy-efficient.

15. Advantages:
• Achieve energy savings by using improved filament technology or reflective coatings.
• Maintain the familiar appearance and instant-on feature of incandescent lamps.
Considerations:
• Energy savings are modest compared to CFLs and LEDs.
1.7.1. Benefits of Energy-Efficient Lamps:
• Reduced Energy Consumption: Energy-efficient lamps consume less electricity,
resulting in lower energy bills.
• Longer Lifespan: Energy-efficient lamps generally last longer, reducing the frequency
of replacements.
• Environmental Impact: Lower energy consumption leads to reduced greenhouse gas
emissions and lower environmental footprint.
• Cost Savings: While initial costs may be higher, long-term savings from reduced energy
consumption and fewer replacements outweigh the initial investment.
1.7.2. Choosing the Right Lamp:
• Consider the desired color temperature and brightness for the intended space.
• Assess the lamp's compatibility with existing fixtures and dimmers (if needed).
• Compare the initial cost with the estimated energy savings over the lamp's lifespan.
• Look for reputable brands with good warranties for consistent performance.
1.8. Luminaires, Wiring, Switching, and Control Circuits:
1.8.1. Luminaires:
• Luminaires are lighting fixtures that contain light sources, reflectors, and lenses to
distribute and control light.
• They come in various designs, shapes, and sizes to suit different applications and
aesthetics.

16. • Luminaires ensure efficient light distribution and protect light sources.
1.8.2. Wiring:
• Proper wiring is essential to safely connect lighting fixtures to power sources.
• Adequate wiring prevents electrical hazards, such as short circuits and overloads.
• Wiring systems include conductors, insulation, grounding, and protective devices.
1.8.3. Switching and Control Circuits:
• Switches control the on/off state of lighting fixtures.
• Control circuits include dimmers, timers, sensors, and smart systems for adjusting
lighting levels and optimizing energy usage.
1.9. Importance of Lighting in Human Life
Lighting holds immense significance in human life, impacting various aspects of our physical,
mental, and emotional well-being. Beyond simply illuminating spaces, lighting influences how
we perceive the world around us and shapes our daily experiences .The importance of lighting
in human life:
1. Visual Comfort and Safety:
• Adequate lighting ensures that we can see and navigate our surroundings safely, reducing
the risk of accidents and falls.
• Proper lighting enhances visibility, making it easier to identify obstacles, read signs, and
distinguish objects in our path.
2. Productivity and Performance:
• Well-designed lighting in workplaces, schools, and other environments enhances focus
and concentration, leading to improved productivity and performance.
• Appropriate lighting reduces eye strain and fatigue, allowing individuals to work or study
comfortably for longer periods.
3. Emotional Well-being and Mood Enhancement:
• Lighting has a profound effect on our emotions and mood. Bright and well-lit
environments are often associated with positive feelings.

17. • Natural light and warm, pleasant lighting can uplift spirits and create a more inviting
atmosphere.
4. Health and Circadian Rhythms:
• Exposure to natural light helps regulate our internal biological clock, known as the
circadian rhythm.
• Proper lighting can help maintain healthy sleep patterns, energy levels, and hormonal
balance.
5. Architectural Enhancement and Aesthetics:
• Lighting serves as a tool for highlighting architectural features, artworks, and design
elements, enhancing the aesthetics of spaces.
• Thoughtful lighting design can create visual interest and transform ordinary spaces into
visually appealing environments.
6. Social Interaction and Communication:
• Proper lighting fosters comfortable social interactions by allowing people to see each
other's facial expressions and gestures.
• In social and public spaces, lighting contributes to a sense of safety and encourages social
engagement.
7. Specialized Environments:
• Lighting plays a critical role in specialized environments such as hospitals, museums,
theaters, and retail stores.
• In hospitals, appropriate lighting supports medical procedures and patient comfort, while
in museums and theaters, it enhances displays and performances.
8. Psychological Impact:
• Certain types of lighting can evoke specific psychological responses. For example, warm
lighting can create a cozy and intimate atmosphere, while bright lighting can evoke energy and
alertness.
9. Safety and Security:
• Outdoor lighting in streets, parking lots, and pathways enhances safety by deterring
criminal activity and providing visibility for pedestrians and drivers.
10. Sense of Time and Place:
• Lighting helps us perceive the passage of time and the transition between day and night.
• It also defines the ambiance of different places, contributing to their unique identities.

18. In essence, lighting is not merely a functional necessity but a powerful tool that affects our
well-being, behavior, and interactions with our surroundings. Thoughtful lighting design takes
into consideration the functional, emotional, and aesthetic aspects of light, creating
environments that enhance our lives in countless ways.
1.10. Dependence of Human Activities on Light:
• Lighting plays a critical role in enabling various human activities, such as reading,
working, and socializing.
• Proper lighting enhances safety, productivity, and well-being
1.11. Quantification and Measurement of Light:
.• Illuminance: Measured in lux (lx), it indicates the amount of light falling on a surface.
• Luminance: Measured in candelas per square meter (cd/m²), it represents the intensity of
light emitted or reflected from a surface.
• Color Temperature: Measured in Kelvin (K), it quantifies the color appearance of light
sources.
• Color Rendering Index (CRI): A scale from 0 to 100, it measures how well a light source
renders colors compared to natural light.
• Footcandles: A unit of illuminance used in the United States, with 1 footcandle equivalent
to 10.764 lux.
1.12. Good and Bad Effects of Lighting:
1.12.1. Good Effects:
• Improved visibility and safety.
• Enhanced productivity and well-being.
• Accentuating architectural features and artworks.
• Creating desired atmospheres and moods.
1.12.2. Bad Effects:
• Glare: Uncomfortable, excessive brightness causing visual discomfort.
• Flicker: Rapid and unintended changes in light intensity.
• Inadequate lighting: Shadows, reduced visibility, and eye strain.

19. 1.13. Artificial Lighting as Substitute to Natural Light:
• Artificial lighting replicates natural light to meet human needs in indoor spaces and at
night.
• It provides consistent illumination regardless of external conditions.
Ability to Control Natural Light:
• Architectural design and window placement allow control over the amount of natural light
entering a space.
• Techniques such as shading, curtains, and blinds regulate light levels.
Production of Light and Physics of Generation of Light:
• Light is produced through various processes, such as incandescence, luminescence, and
electrical discharges.
• Physics principles govern the interaction between energy and matter to create visible light.
Properties of Light:
• Light behaves as both a particle (photon) and a wave (electromagnetic radiation).
• It travels in straight lines until interacting with an object or medium.
Visual Perception and Optical Radiation Hazards:
• Visual perception involves the brain processing visual signals from the eyes to form a
coherent image.
• Optical radiation hazards include excessive brightness, ultraviolet (UV) radiation, and blue
light exposure, which can cause eye strain and health issues.
Lighting, an integral part of human life, influences visual perception, safety, productivity, and
well-being. Luminaires, wiring, switching, and control circuits ensure effective illumination.
Understanding the optical systems of the human eye, quantification of light, and the good and
bad effects of lighting guides the design of optimal lighting solutions. Whether through natural
or artificial sources, lighting profoundly affects our daily experiences and activities

20. Lighting fixtures:
 Flush Mount Fixtures:
Description: These fixtures are mounted directly to the ceiling, and the base is flush
with the ceiling surface.
Use: Common in spaces with low ceilings or where a sleek and unobtrusive look is
desired.
 Semi-Flush Mount Fixtures:
Description: Similar to flush mount fixtures, but they hang down slightly, usually with
a short stem or chain.
Use: Provides a bit more decorative flair compared to flush mounts, suitable for
medium-height ceilings.
 Chandeliers:
Description: Ornate, hanging light fixtures with multiple arms and branches, often
adorned with crystals or other decorative elements.
Use: Typically used in dining rooms, entryways, or large living spaces for a touch of
elegance.
 Pendant Lights:
Description: Single light fixtures that hang from the ceiling, often suspended by a cord,
chain, or rod.
Use: Perfect for task lighting over kitchen islands, dining tables, or as decorative
elements in various spaces.
 Ceiling Fans with Lights:
Description: Ceiling fans that incorporate built-in light fixtures.
Use: Provides both lighting and air circulation in rooms.
 Track Lighting:
Description: A system where multiple light fixtures are mounted on a track, allowing
for adjustable and directional lighting.
Use: Ideal for highlighting artwork, accenting spaces, or providing task lighting.

21.  Wall Sconces:
Description: Fixtures that are mounted on walls, directing light upward or downward.
Use: Provides ambient or accent lighting and is often used in hallways, bathrooms, or
as decorative elements.
 Recessed Lighting:
Description: Light fixtures installed into the ceiling, creating a clean and minimalist
look.
Use: Suitable for general lighting or accent lighting, and commonly used in various
settings.
 Floor Lamps:
Description: Tall standing lamps that provide ambient or task lighting.
Use: Adds flexibility to the lighting design and is movable to different locations.
 Table Lamps:
Description: Lamps designed to sit on tables or other surfaces.
Use: Provides localized lighting for reading or accent lighting in living rooms,
bedrooms, or offices.
 Under Cabinet Lighting:
Description: Lighting fixtures installed beneath kitchen cabinets.
Use: Offers task lighting for food preparation and adds a decorative touch to the
kitchen.
 Outdoor Lighting Fixtures:
Description: Lights designed for exterior spaces, including wall-mounted fixtures, post
lights, and landscape lighting.
Use: Illuminates outdoor areas such as entryways, patios, and gardens.