Waveguide Construction: Identify the Incorrect Statement For metallic waveguides used at microwave frequencies, which of the following statements is wrong?

Introduction / Context:
Waveguides are hollow metallic structures guiding TE/TM modes. Fabrication choices affect loss, bandwidth, and durability. Knowledge of correct construction principles avoids high-loss designs.

Given Data / Assumptions:

• Normal microwave bands (e.g., X, Ku) with good conductors.
• Interest in qualitative correctness of statements about materials, geometry, and skin depth.

Concept / Approach:

At microwave frequencies, skin depth δ is very small; to minimize conductor loss and ensure mechanical strength, wall thickness is made many skin depths, not “very small compared to δ”. Rectangular and circular cross-sections are standard; brass, aluminium, and copper-plated surfaces are commonly used. Air is the usual dielectric fill to keep loss low.

Step-by-Step Solution:

Verification / Alternative check:

Skin-effect formulas show conductor loss varies with surface resistance; plating with high-conductivity copper/silver reduces loss and is common practice.

Why Other Options Are Wrong:

Only D contradicts standard engineering practice; the others reflect widely used constructions.

Common Pitfalls:

Misinterpreting “skin depth” and assuming any thickness suffices; in reality, multiple skin depths are required for low loss and structural integrity.

Final Answer:

The wall thickness is very small as compared to skin depth