91Ó°ÊÓ

Distinguish between materials that are opaque, translucent, and transparent in terms of their appearance and light transmittance.

(a) Briefly describe the phenomenon of electronic polarization by electromagnetic radiation. (b) What are two consequences of electronic polarization in transparent materials

Briefly explain why metals are opaque to electromagnetic radiation having photon energies within the visible region of the spectrum.

In ionic materials, how does the size of the component ions affect the extent of electronic polarization?

Can a material have an index of refraction less than unity? Why or why not?

Compute the velocity of light in diamond, which has a dielectric constant \(\epsilon_{r}\) of 5.5 (at frequencies within the visible range) and a magnetic susceptibility of \(-2.17 \times 10^{-5}\).

Briefly describe the phenomenon of dispersion in a transparent medium.

Zinc selenide has a band gap of \(2.58 \mathrm{eV}\). Over what range of wavelengths of visible light is it transparent?

Briefly explain why the magnitude of the absorption coefficient \((\beta \text { in Equation } 21.18)\) depends on the radiation wavelength.

The transmissivity \(T\) of a transparent material 15 \(\mathrm{mm}\) thick to normally incident light is \(0.80 .\) If the index of refraction of this material is \(1.5,\) compute the thickness of material that will yield a transmissivity of \(0.70 .\) All reflection losses should be considered.