What phenomenon occurs on a transmission line when there is a load mismatch?

• A. Standing waves
• B. Increased radiation along the line
• C. No effect
• D. Phase cancellation only at the source

Answer: (A)

When a load doesn’t match the transmission line, part of the traveling wave is reflected back toward the source. The forward wave and this reflected wave meet and interfere, creating a standing wave pattern along the line. This means the voltage and current have fixed nodes (points of minimum) and antinodes (points of maximum) along the line, rather than a simple, uniform traveling wave. The extent of the mismatch is described by the reflection coefficient and the standing wave ratio (VSWR), which quantify how much of the power is reflected versus delivered to the load. Because energy is reflected, not all power reaches the load, which is a hallmark of a mismatched line. While there can be some radiation changes in practical setups, the key phenomenon you’re looking for is the standing wave along the line due to interference from reflections.