Topic: Electromagnetics
If the waveguide cross-section of a square waveguide with $TE_{11}$ propagation mode is gradually deformed into a circle, then the corresponding circular waveguide mode will be
- A. $TE_{11}$
- B. $TE_{10}$
- C. $TE_{21}$
- D. $TE_{12}$
Answer: C. $TE_{21}$
Explanation: Based on the official answer key, the correct option is (c) $TE_{21}$. No detailed derivation is provided in the reference.