Module 1-1Nature andProperties ofLight

Introduction Section1Photonics 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 2This 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 3See page 9 of PDF text

Scenario Section 4Read

Basic Concepts Section 5What 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.◦particle when it acts like discrete

clumps of energy—which we call photons.

Basic Concepts Section 5When 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.

Basic Concepts Section 5Visible light is part of an extensive

electromagnetic spectrum. This vast spectrum or array of

electromagnetic energy contains ◦X rays◦Microwaves◦Radio waves◦Infrared and ultraviolet light◦Gamma rays,◦and “visible light.”

Basic Concepts Section 5 Source:

http://imagine.gsfc.nasa.gov/Images/science/EM_spectrum_compare_level1_lg.jpg

Basic Concepts Section 5Whether we regard light as a wave or

as a stream of discrete particles, we use the following properties to describe it:◦Wavelength◦Frequency◦Period◦Amplitude◦Speed◦Phase◦Coherence◦Polarization◦Energy

Basic Concepts Section 5The Wave Properties of LightA 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

Basic Concepts Section 5Figure 1.1

Basic Concepts Section 5The 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)

Basic Concepts Section 5Figure 1.2 illustrates the same

wave as a function of time at a fixed position along the wave.

Basic Concepts Section 5The 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).

Basic Concepts Section 5Frequency 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

Basic Concepts Section 5The unit of frequency is

cycles/second, or hertz, and may be abbreviated as Hz, s-1, or /s.

Period is measured in seconds and wavelength in meters.

Basic Concepts Section 5The 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

Basic Concepts Section 5Table 1.1 page 13

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)

Basic Concepts Section 5The 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)

Basic Concepts Section 5See examples 1, 2 and 3 on page

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