Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

GTBL042-19 GTBL042-Callister-v2 September 17, 2007 17:39

Revised Pages

Learning Objectives

After careful study of this chapter you should be able to do the following:

1.Compute the energy of a photon given its

frequency and the value of Planck’s constant.

2.Briefly describe electronic polarization that

results from electromagnetic radiation-atomic

interactions. Cite two consequences of electronic

polarization.

3.Briefly explain why metallic materials are opaque

to visible light.

4.Defineindex of refraction.

5.Describe the mechanism of photon absorption for

(a) high-purity insulators and semiconductors,

and (b) insulators and semiconductors that

contain electrically active defects.

6.For inherently transparent dielectric materials,

note three sources of internal scattering that can

lead to translucency and opacity.

7.Briefly describe the construction and operation

of ruby and semiconductor lasers.

19.1 INTRODUCTION

By “optical property” is meant a material’s response to exposure to electromagnetic

radiation and, in particular, to visible light. This chapter first discusses some of the ba-

sic principles and concepts relating to the nature of electromagnetic radiation and its

possible interactions with solid materials. Next to be explored are the optical behav-

iors of metallic and nonmetallic materials in terms of their absorption, reflection, and

transmission characteristics. The final sections outline luminescence, photoconduc-

tivity, and light amplification by stimulated emission of radiation (laser), the practical

utilization of these phenomena, and optical fibers in communications.

Basic Concepts

19.2 ELECTROMAGNETIC RADIATION

In the classical sense, electromagnetic radiation is considered to be wave-like, consist-

ing of electric and magnetic field components that are perpendicular to each other

and also to the direction of propagation (Figure 19.1). Light, heat (or radiant en-

ergy), radar, radio waves, and x-rays are all forms of electromagnetic radiation. Each

is characterized primarily by a specific range of wavelengths, and also according to the

technique by which it is generated. Theelectromagnetic spectrumof radiation spans

the wide range fromγ-rays (emitted by radioactive materials) having wavelengths

on the order of 10−^12 m (10−^3 nm), through x-rays, ultraviolet, visible, infrared, and

finally radio waves with wavelengths as long as 10^5 m. This spectrum, on a logarithmic

scale, is shown in Figure 19.2.



H

Position



Figure 19.1 An

electromagnetic

wave showing

electric fieldeand

magnetic fieldH

components, and the

wavelengthλ.

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