Module 1-1
Nature and
Properties of
Light
Introduction Section1
 Photonics is a scientific term that
refers to phenomena, components and
devices like optics, lasers, fiber-optics and
electro-optics.
 Applications
and Careers read
Prerequisites Section 2
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This module requires a basic
understanding of high school algebra,
geometry, trigonometry, general scientific
nomenclature, the scientific process, unit
conversions, and basic concepts in
elementary physics and chemistry.
Objectives Section 3
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See page 9 of PDF text
Scenario Section 4
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Read
Basic Concepts Section 5
What is light?
 The safest answer we can give at this time
is that light seems to have both wave and
particle properties, and that it is basically a
form of electromagnetic energy.
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◦ particle when it acts like discrete clumps of
energy—which we call photons.
Basic Concepts Section 5
When it travels through space or passes
through small openings, it behaves like a
wave, made up of connected electric and
magnetic fields, vibrating and traveling
together.
 When it reflects off of mirrors or is
absorbed by materials, it seems to take on
the properties of particles or packets of
energy.
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Basic Concepts Section 5
Visible light is part of an extensive
electromagnetic spectrum.
 This vast spectrum or array of
electromagnetic energy contains
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X rays
Microwaves
Radio waves
Infrared and ultraviolet light
Gamma rays,
and “visible light.”
Basic Concepts Section 5
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Source:
http://imagine.gsfc.nasa.gov/Images/science/EM_spectrum_compare
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Basic Concepts Section 5
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Whether we regard light as a wave or as
a stream of discrete particles, we use the
following properties to describe it:
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Wavelength
Frequency
Period
Amplitude
Speed
Phase
Coherence
Polarization
Energy
Basic Concepts Section 5
The Wave Properties of Light
 A wave is a disturbance that transmits
energy from one point to another.
 Light, as it travels through space, can be
described as a wave phenomenon.
 Figure 1.1 illustrates a wave traveling to
the right at one instant of time. (p.12) and
next slide
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Basic Concepts Section 5
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Figure 1.1
Basic Concepts Section 5
The displacement is the vertical
distance measured from the equilibrium
position at any point along the wave.
 The amplitude is the maximum
displacement of the wave.
 Wavelength is defined as “the distance
over which the wave repeats itself” and is
represented by the Greek letter lambda
(λ)
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Basic Concepts Section 5
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Figure 1.2 illustrates the same wave as a
function of time at a fixed position along
the wave.
Basic Concepts Section 5
The period is the interval of time over
which the wave repeats itself; the time
required for one complete cycle of the
wave. The symbol for the period is (T).
 The frequency of the wave is the
number of cycles of the wave in one
second and is represented by the Greek
letter nu (ν).
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Basic Concepts Section 5
Frequency and period are related by
Equations 1-1 and 1-2:
 ν = 1/T
Equation (1-1)
 T = 1/ν Equation (1-2)
where: T = Period in seconds (s)
ν = Frequency in hertz (Hz)
Page 13
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Basic Concepts Section 5
The unit of frequency is cycles/second,
or hertz, and may be abbreviated as Hz, s1, or /s.
 Period is measured in seconds and
wavelength in meters.
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Basic Concepts Section 5
The unit micrometer (10−6 m) is a widely
used unit of length and also is called a
“micron.” The micron is represented by
either μm or m, with μm preferred.
 A common wavelength unit not included
in this table is the angstrom
1 Angstrom = 10−10 m
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Basic Concepts Section 5
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Table 1.1 page 13
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Movie 1.2 Engineering Notation, page 13
Basic Concepts Section 5
The speed or velocity of a wave is the distance
traveled in one cycle, or the wavelength divided
by the time required for one cycle (the period).
 Equations 1-3 and 1-4 are expressions for wave
speed V.
 V = λ/T
Equation (1-3)
 V = λν
Equation (1-4)
where:
T = Period of the wave (seconds, s)
λ = Wavelength (meters, m)
ν = Frequency of the wave (Hz, 1/s)
V = Speed of the wave (m/s)
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Basic Concepts Section 5
The speed of light traveling through a
vacuum is 3 × 108 m/s and is expressed by
the symbol c, which can be substituted
for V (velocity) in Equation 1-4 to give
Equations 1-5, 1-6, and 1-7.
 c = λν Equation (1-5)
 λ = c/ν Equation (1-6)
 ν = c/λ Equation (1-7)
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Basic Concepts Section 5
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See examples 1, 2 and 3 on page 14