91Ó°ÊÓ

Visible light having a wavelength of \(5 \times 10^{-7} \mathrm{~m}\) appears green. Compute the frequency and energy of a photon of this light.

Distinguish among 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 a positive 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 \(-2.17 \times 10^{-5}\)

Using the data in Table \(21.1\), estimate the dielectric constants for silica glass (fused silica), soda-lime glass, polytetrafluoroethylene, polyethylene, and polystyrene, and compare these values with those cited in the following table. Briefly explain any discrepancies. \begin{tabular}{lc} \hline Material & Dielectric Constant (1 MHz) \\ \hline Silica glass & \(3.8\) \\ \hline Soda-lime glass & \(6.9\) \\ \hline Polytetrafluoroethylene & \(2.1\) \\ \hline Polyethylene & \(2.3\) \\ \hline Polystyrene & \(2.6\) \\ \hline \end{tabular}

Briefly describe the phenomenon of dispersion in a transparent medium.

Briefly explain how reflection losses of transparent materials are minimized by thin surface coatings.