Question

The dielectric constant of a material at ultraviolet frequencies is mainly due to

• A. dipolar polarizability
• B. ionic polarizability
• C. electronic polarizability
• D. interfacial polarizability

Hint:

At high frequencies such as ultraviolet light, the dielectric behavior of a material is mainly due to the electronic polarizability, which is the displacement of electron clouds in atoms or molecules.

Answer 1

The Correct Option is C

The dielectric constant of a material is a measure of how much a material can polarize in response to an applied electric field. This polarization affects how the material responds to electromagnetic radiation. The dielectric constant depends on the frequency of the applied field, and different mechanisms of polarization dominate at different frequencies. At ultraviolet (UV) frequencies, the material's polarization response is primarily governed by the electronic polarizability. This is because at such high frequencies, the electronic cloud around atoms or molecules is able to move in response to the electric field, and this movement is fast enough to respond to the oscillating electromagnetic fields of UV light. - Dipolar polarizability involves the alignment of permanent dipoles in the material with the applied electric field. However, this mechanism is more significant at lower frequencies, especially for polar molecules. - Ionic polarizability involves the displacement of ions in an ionic material. This also typically occurs at lower frequencies, where ions can move freely and respond to electric fields. - Electronic polarizability is the displacement of electron clouds in atoms or molecules. This mechanism is dominant at high frequencies like UV because it responds very quickly to the oscillating electric field, making it the main contributor to dielectric behavior at these frequencies. Therefore, at ultraviolet frequencies, the dielectric constant is primarily due to electronic polarizability, which corresponds to option (C).
Final Answer: (C) electronic polarizability