Light and Optics

Principles and Practices

Abdul Al-Azzawi

• Publisher: CRC Press
• Year: 2018
• eBook ISBN: 9781351838146
• Topic: Physical Sciences
• Subtopic: Optics & Light

Since the invention of the laser, our fascination with the photon has led to one of the most dynamic and rapidly growing fields of technology. As the reality of all-optical systems quickly comes into focus, it is more important than ever to have a thorough understanding of light and the optical components used to control it. Comprising chapters drawn from the author's highly anticipated book Photonics: Principles and Practices, Light and Optics: Principles and Practices offers a detailed and focused treatment for anyone in need of authoritative information on this critical area underlying photonics. Using a consistent approach, the author leads you step-by-step through each topic. Each skillfully crafted chapter first explores the theoretical concepts of each topic, and then demonstrates how these principles apply to real-world applications by guiding you through experimental cases illuminated with numerous illustrations. The book works systematically through light, light and shadow, thermal radiation, light production, light intensity, light and color, the laws of light, plane mirrors, spherical mirrors, lenses, prisms, beamsplitters, light passing through optical components, optical instruments for viewing applications, polarization of light, optical materials, and laboratory safety. Containing several topics presented for the first time in book form, Light and Optics: Principles and Practices is simply the most modern, comprehensive, and hands-on text in the field.

1	The Nature of Light

1.1 INTRODUCTION

Throughout history, humankind has been fascinated with the properties and behaviour of light. Light from the sun served as a catalyst in the formation of life on Earth. Solar and lunar light provided humanity with the celestial timepieces required to measure time.

We live in a world bathed in light. Light is one of the most familiar things in our lives. We see things with eyes that sense the intensity (brightness) and wavelength (colour) of light. We experience light in a variety of other ways as well. For example, we sense radiant heat when our skin is near a warm object. This is due to our skin’s reaction to infrared radiation.

We learn almost all of what we know about the world around us from the interaction of materials with electromagnetic waves. Often, the word light is used a little more broadly to include electromagnetic waves, such as in the ultraviolet and infrared waves that are just outside the visible range.

Much of what we know about light has been discovered during the past five centuries. Initially, light was understood to be a particle. Light is now widely understood to be one part of a much larger electromagnetic spectrum. Photons, the smallest resolvable quanta of light, were initially described using particle theory; however, a wave model has since been widely adopted. In the context of the wave model, photons are energy packets moving through space and time.

1.2 THE EVOLUTION OF LIGHT THEORY

In the 17th century, light was considered to be stream of particles that were emitted by a light source. These particles stimulate the sense of sight when entering the eye. The English physicist and mathematician Isaac Newton (1642–1727) was the inventor of the particle theory of light. Newton regarded rays of light as streams of very small particles emitted from a source of light and travelling in straight lines. Newton was able to provide a simple explanation for some known experimental facts concerning the nature of light, specifically, the laws of reflection and refraction.

Most scientists accepted Newton’s particle theory of light. However, during Newton’s lifetime, another theory was proposed by the Dutch physicist and astronomer Christian Huygens (1629–1695). In 1678, Huygens presented his theory, in which light might be some sort of wave motion. His experiment demonstrated that when the two beams of light intersected, they emerged unchanged, just as in the case of two water or sound waves. Huygens was able to adopt a wave theory of light to derive the laws of reflection and refraction, and to explain double refraction in calcite. This wave theory did not receive immediate acceptance from the scientific community for several reasons. The only waves known at that time were sound and water. It was known that these waves travelled through some sort of medium. On the other hand, light could travel to us from the sun through the vacuum of space. It was agreed that if light was some form of wave motion, the waves would be able to bend around obstacles and corners. This bending is easily observed with both water and sound waves. In this case, it would be easy to see the light around corners. It is now known that light does actually bend around the edges of objects; this phenomenon is known as the diffraction of light, which will be discussed later in this book.

In 1660, experimental evidence for the diffraction of light was discovered by Francesco Grimaldi (1618–1663). Most scientists still rejected the wave theory and continued to adhere to Newton’s particle theory for more than a century.

In 1801, the first clear demonstration of the wave theory of light was provided by the English physician, Thomas Young (1773–1829). He performed a significant experiment, which showed that light exhibits interference behaviour. There are two types of interference: constructive and destructive. When two waves are moving in the same direction, the vertical displacement (amplitude) of the combined waveform is greater than that of either wave; this situation is referred to as constructive interference. Conversely, if one wave has a negative displacement, the two waves work to cancel each other when they overlap, and the amplitude of the combined waveform is smaller than that of either wave. This is referred to as destructive interference. Light interference behaviour will be explained later in this book. Most scientists accepted the wave theory of light and more theoretical and experimental work was conducted to further explore it.

In 1821, the French physicist Augustin Fresnel (1788–1827) published the results and analysis of a number of detailed experiments, which dealt with interference of polarized light and diffraction phenomena. He obtained circularly polarized light by means of a special glass prism now known as a Fresnel rhomb. For each of the two components of the polarized light, Fresnel developed the Fresnel Equations, which give the amplitude of light reflected and transmitted at a plane interface separating two optical media.

In 1850, Jean Foucault (1791–1868) provided further evidence of the inadequacy of the particle theory by showing that the speed of light in liquids is less than that in air. According to the particle model of light, the speed of light would be higher in a glass and liquid than in air. Further experimental and theoretical developments during the 19th century led to the general acceptance of the wave theory of light.

In 1873, the most important development concerning the theory of light was the work of a Scottish physicist, James C. Maxwell (1831–1879). Maxwell asserted that light was a form of high-frequency electromagnetic wave. Working in the field of electricity and magnetism, Maxwell created known principles in his set of four Maxwell Equations. These equations predict the speed of an electromagnetic wave in the ether; this turned out to be the true measured speed of light. His theory predicted that these waves should have a speed of about 3×10⁸ m/s. Within experimental error, his predicted value is nearly equal to the speed of light measured by sophisticated instruments today. From then on, light was viewed as a particular region of the electromagnetic spectrum of radiation.

In 1887, Heinrich Hertz (1857–1894), a German physicist and pioneering investigator of electromagnetic waves, provided experimental confirmation of Maxwell’s theory by producing and detecting electromagnetic waves. Hertz also defined the frequency. Furthermore, Hertz and other scientists and investigators showed that these waves exhibited reflection, refraction, and all the other characteristic properties of waves.

Although the classical theory of electricity and magnetism was able to explain most known properties of light, some subsequent experiments could not be explained by assuming that light is a wave. The most striking discovery of the experiments is the photoelectric effect, which was discovered by Hertz. The photoelectric effect is the ejection of electrons from a metal when its surface is exposed to light. As one example of the difficulties that arose, experiments showed that the kinetic energy of an ejected electron is independent of the light intensity. This was in contradiction to the wave theory, which held that a more intense beam of light should add more energy to the electron. In 1905, an experiment demonstrating of this phenomenon was proposed by Albert Einstein (1879–1955), a German-Swiss physicist. In 1900, Einstein’s theory used the concept of the quantum theory developed by Max Planck (1858–1947), a German theoretical physicist. The quantization model assumes that the energy of a light wave is present in bundles of energy called photons. Therefore, the energy is said to be quantized. According to Einstein’s theory, the energy of a photon is proportional to the frequency of the electromagnetic wave. The energy of a photon can be defined by Equation (1.1):

$E=n\left(hf\right)n=0,1,2,3,\mathrm{\dots }$

(1.1)

where

n is a positive integ...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Chapter 1 The Nature of Light
• Chapter 2 Light and Shadows
• Chapter 3 Thermal Radiation
• Chapter 4 Light Production
• Chapter 5 Light Intensity
• Chapter 6 Light and Colour
• Chapter 7 Laws of Light
• Chapter 8 Plane Mirrors
• Chapter 9 Spherical Mirrors
• Chapter 10 Lenses
• Chapter 11 Prisms
• Chapter 12 Beamsplitters
• Chapter 13 Light Passing through Optical Components
• Chapter 14 Optical Instruments for Viewing Applications
• Chapter 15 Polarization of Light
• Chapter 16 Optical Materials
• Chapter 17 Photonics Laboratory Safety
• Appendix A: Details of the Devices, Components, Tools, and Parts
• Appendix B: International System of Units (SI)
• Appendix C: Lighting Lamps
• Glossary
• Index