What is the reflection coefficient expression and when is power transfer best?

• A. Γ = (ZL + Z0)/(ZL - Z0) and reflections are minimized by exact impedance ratios
• B. Γ is zero when ZL equals 2Z0
• C. Best power transfer occurs when ZL equals Z0
• D. Reflection effects can be ignored when frequency is low

Answer: (C)

The key idea is how a transmission line handles power through impedance matching. The reflection coefficient, which tells you how much of the wave is reflected, is given by Γ = (ZL - Z0) / (ZL + Z0). When the load matches the line, ZL equals Z0, so Γ = 0 and there are no reflections; all the incident power is delivered to the load.

This is why the best power transfer occurs when ZL equals Z0: it eliminates reflections and maximizes the power that reaches the load. The other statements misstate either the reflection formula or the condition for zero reflection, or they oversimplify the role of frequency in reflections.