Department of Technical Education
Andhra Pradesh
Name
Designation
Branch
Institute
Year/Semester
Subject
Subject Code
Topic
Duration
Sub Topic
Teaching Aids
Revised By
: P. Balanarsimlu
: Lecturer
: Electrical Engineering
: Govt. Polytechnic Nizamabad
: VI Semester
: Electrical Utilisation and Traction
: EE605A
: Electric Lighting
: 50 Min
: Nature of Light and its Propagation
: PPT, Diagrams, Animation
: K. Chandra Sekhar, L/ EEE, GPT, HYD
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Objectives
On completion of this class you would be able to
know
• The Principles, Nature and its Propagation of Lighting
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Known To Unknown
• What is light ?
• Importance of Light
• Electrical Light
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Introduction
• Electrical power plays an important role in our day to
day life and it became part of our life
• Electrical energy is used in industries, agriculture,
transportation, household etc.
• Utilization of Electrical power became back bone of
industrial World for Electric lighting, heating, welding,
drives, controls and traction
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Light
• Light is an electromagnetic radiation
• The natural sources of light are the sun and the stars
• Sun emits both heat and light energy at a very
tremendous rate
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•The natural source of light is the sun and stars.
Fig.1
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•The natural source of light are the sun and stars.
Fig.2
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Electrical Lighting
Work which can be done in day time, can also
be done equally by means of artificial lighting
during night times , which is possible with the
help of electricity
Fig.3
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Electrical Lighting
The need of understanding illumination engineering is to
make the visual environment by reducing strain on the
eyes and nervous system
Fig.4
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Electrical Lighting
• In the sphere of industrialization, good illumination
ensures increased production and reduced fatigue on
workers
• More lighting causes discomfort and less lighting
causes strain on eyes
• So it is necessary to design the lighting scheme in
such a way that illumination is proper for proper
places
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Fig.5a
Fig.5b
It is necessary to design the lighting scheme in such a way
that illumination is proper for proper places.
Fig.5c
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Fig.5d
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Nature of Light and its Propagation
• Light is a form of radiant energy, its nature depends
upon the temperature of the hot body
• A hot body of about 5000C to 8000C becomes a red
hot and about 25000Cto 30000C becomes white hot
• In both the cases a part of radiation is in the form of
light
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Nature of Light and its Propagation
Fig.6
• A part of radiation is in the form of light
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Nature of Light and its Propagation
Fig.7
• It is understood that light is a form of energy, which can
be radiated like heat and is converted from heat only
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Nature of Light and its Propagation
• Light radiations can propagate like electro-magnetic
waves through a medium in the form of transverse
waves
Fig.8
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Nature of Light and its Propagation
• The propagation velocity of the radiant energy in a
medium is
3 X 108 m/sec
• Different light waves have different frequencies, but the
velocity is same
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Nature of Light and its Propagation
• The different frequencies of light waves produce
different Colour sensation on human eye
Fig.9
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Nature of Light and its Propagation
• The band width of visible frequencies is
4.3X1014 Hz to 7.5X1014 Hz
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Electromagnetic Spectrum
NATURE OF THE WAVES
Cosmic rays
FREQUENCY
in Hz
3X1022
Gamma, X rays
Ultra violet
VISIBLE LIGHT
Infrared
Radar , TV
and Radio
Fig.10
3X1020
WAVE LENGTH
in meters
10-14
-12 14
7.5 X1010
Hz
3X1018
10-10
3X1016
10-8
3X1014
10-6
3X1012
10-4
3X1010
10-2
4.3 X 1014 Hz
3X108
1
3X106
102
3X104
104
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Nature of Light and its Propagation
• The range of wave lengths can perceive sensation of
Colour on human eye is 4000 A0 to 7500A0
(0.004mm to 0.0075mm)
Fig.11
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Nature Of Light and Its Propagation
Short wave length
--- Violet and Blue
Medium wavelength
--- Green Yellow and Orange
Long Wave length
--- Red
Fig.12
The sensitivity percentage of eye varies with respect to
wave length
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Summary
So far we have discussed about
•
•
•
•
•
•
Natural Source of Light
Nature of Light
Propagation of Light
Frequency and Wave Length of Light
Electromagnetic spectrum
Frequency band of Visible Light
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Quiz
1. The Natural Source of Light is
A) Sun
B) Candle
C) Kerosene lamp
D) Gas light
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Quiz
2. Which of the following frequency belongs to light?
A) 108Hz
B) 1012Hz
C) 1014Hz
D) 106Hz
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Quiz
3. The Velocity of Light is
A) 3X106 m/sec
C) 3X104 m/sec
B) 3X1012 m/sec
D) 3X108 m/sec
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Quiz
4. The range of wavelength of visible light is
A) 400A0 to 750A0
B) 4000A0 to 7500A0
C) 400A0 to 7500A0
D) 40A0 to 75A0
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Frequently Asked Questions
1)
What is light ?
2)
Explain the nature of light and its propagation
3)
Draw the electromagnetic spectrum and show the
visible light band
4)
Explain about Colour sensitivity on human eye
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THANK YOU
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