Chapter 21: Problem 3

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

Short Answer

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Answer: Two consequences of electronic polarization in transparent materials are the increase in the refractive index and dispersion. The refractive index is affected by electronic polarization, leading to a modification of the material's optical response. Dispersion results from the material responding differently to various wavelengths of incident light, causing the separation of colors within the spectrum.

Step by step solution

(a) Electronic Polarization by Electromagnetic Radiation

Electronic polarization occurs when an external electric field (created by electromagnetic radiation) interacts with a dielectric material or atoms/molecules of the material. The electric field displaces the negative electrons from their equilibrium positions relative to the positive atomic nucleus, thereby creating a dipole moment within the material. This dipole moment is proportional to the applied electric field, as described by the linear expression P = ε_0χ_eE, where P is the polarization, ε_0 is the permittivity of free space, χ_e is the electric susceptibility, and E is the applied electric field.

(b) Consequence 1: Refractive Index

One of the consequences of electronic polarization in transparent materials is the increase in the refractive index. The refractive index (n) is a measure of the speed at which light propagates through a material compared to its propagation speed in vacuum. Due to the electronic polarization, the optical response of the material changes, leading to the modification of the refractive index. The relationship between the refractive index and the electric susceptibility is given by n^2 = 1 + χ_e, where χ_e represents the contribution of electronic polarization to the total polarization.

(b) Consequence 2: Dispersion

Another consequence of electronic polarization in transparent materials is dispersion. Dispersion is the phenomenon where different wavelengths of light are refracted (i.e., deviated from their original path) to varying degrees, resulting in the separation of colors within the spectrum. Due to electronic polarization, the material responds differently to various wavelengths of incident light, and hence, the refractive index becomes wavelength-dependent. This dependence leads to the manifestation of dispersion, which plays a crucial role in optical devices such as lenses, prisms, and spectrometers.

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

Short Answer

Step by step solution

(a) Electronic Polarization by Electromagnetic Radiation

(b) Consequence 1: Refractive Index

(b) Consequence 2: Dispersion

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