CHAPTER 19
OPTICAL PROPERTIES
LEARNING OBJECTIVES
1. Cite the wavelength range for visible light radiation.
2. Note the relationship between the velocity of electromagnetic radiation in a vacuum, and vacuum values of the electric permittivity and magnetic permeability.
3. Given the velocity of electromagnetic radiation in a vacuum as well as the radiation frequency, compute the radiation wavelength.
4. Define photon.
5. Compute the energy of a photon given its frequency and the value of Planck's constant.
6. List three phenomena that may occur with light radiation as it passes from one medium into another.
7. Cite distinctions between optical transparency, translucency, and opacity.
8. (a) Briefly describe electronic polarization that results from electromagnetic radiation-atomic interactions.
(b) Cite two consequences of electronic polarization.
9. Briefly explain how electromagnetic radiation may be absorbed by electron transitions.
10. Briefly explain why metallic materials are opaque to visible light.
11. Note what determines the color of metallic materials.
12. Define index of refraction.
13. Calculate the index of refraction for a material given values of its dielectric constant and relative magnetic permeability.
14. Note the influence of atomic/ionic size on index of refraction.
15. Calculate the reflectivity at an interface for normally incident light given the indexes of refraction for the media on both sides of the interface.
16. For high-purity insulators and semiconductors:
(a) describe the mechanism of photon absorption;
(b) explain how the magnitude of the band gap energy influences photon absorption;
(c) cite band gap energy values for which there is no absorption of visible light radiation; and
(d) cite band gap energy values for which there is only partial absorption of visible light radiation.
17. For insulators and semiconductors that contain electrically active defects:
(a) describe the mechanism of photon absorption;
(b) cite two decay paths that are possible as excited electrons return to their ground states.
18. Calculate the intensity of nonabsorbed radiation that passes through a transparent medium of specified thickness, given the intensity of nonreflected radiation incident on the front face, as well as the absorption coefficient for the particular medium.
19. Determine the intensity of radiation that emerges from the back face of a transparent solid of specified thickness, give the intensity of radiation that impinges on the front face, and, in addition, values of the material's reflectance and absorption coefficient.
20. (a) Briefly explain why some semiconducting materials appear colored.
(b) Now explain the source of color in many insulating materials.
21. (a) For inherently transparent dielectric materials, note three sources of internal scattering that can lead to translucency and opacity.
(b) Briefly explain why internal scattering occurs for each of these sources.
22. Briefly explain why amorphous materials are normally transparent.
23. (a) Describe the phenomena of luminescence and electroluminescence.
(b) Distinguish between fluorescence and phosphorescence.
24. Briefly describe the phenomenon of photoconductivity.
25. Briefly describe the operation of a semiconductor light-emitting diode.
26. Briefly describe the construction of and operation of (a) the ruby laser, and (b) the semiconductor laser.
27. List and describe the functions of various components for an optical fiber communications system.
28. Explain the transmission of digitized signals through optical fibers.
29. Note and briefly explain functions of the several components that are found in an optical fiber.
30. Explain what precautions are taken to minimize scattering and attenuation of a light beam that passes through an optical fiber.