Dielectric Losses in Liquids and Glasses – Assertion–Reason Assertion (A): Dielectric losses occur in liquids and glassy (amorphous) substances under alternating electric fields. Reason (R): Orientation polarization in many substances is frequency dependent.

Introduction / Context:
Dielectric loss is the conversion of electrical energy into heat within an insulating material when subjected to alternating fields. Liquids and glasses often exhibit significant losses due to molecular orientation dynamics and relaxation processes that cannot follow rapid field reversals without phase lag.

Given Data / Assumptions:

• Alternating electric field applied to polar or partially polar media.
• Orientation (dipolar) polarization present for molecules with permanent dipole moments.
• Viscous media where rotational diffusion is finite (non-instantaneous).

Concept / Approach:

Orientation polarization responds to the applied field with a characteristic relaxation time τ. When the excitation frequency is comparable to 1/τ, the dipoles lag behind the field, introducing a quadrature component of polarization and thus energy dissipation per cycle (dielectric loss). Liquids and glasses, with their molecular mobility constraints and distribution of relaxation times, show pronounced frequency-dependent loss tangents.

Step-by-Step Solution:

Verification / Alternative check:

Dielectric spectroscopy reveals relaxation peaks (Debye or non-Debye) in loss vs frequency plots for many liquids and glasses, confirming the explanation.

Why Other Options Are Wrong:

• R false: contradicted by extensive experimental data.
• R not explanatory: it precisely explains the mechanism (frequency-dependent orientation).

Common Pitfalls:

Confusing electronic/atomic polarization (nearly instantaneous, low loss) with orientation polarization; neglecting temperature dependence of τ which shifts loss peaks.

Final Answer:

Both A and R are true and R is correct explanation of A