Nature and Properties of Light 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 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 See page 9 of PDF text

Scenario Section 4 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. 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.

Basic Concepts Section 5 Visible 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 5 Whether 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 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

Basic Concepts Section 5 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)

Basic Concepts Section 5 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).

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

Basic Concepts Section 5 The 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 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

Basic Concepts Section 5 Table 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 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)

Basic Concepts Section 5 See examples 1, 2 and 3 on page 14