Which statement describes what happens at an interface with a large impedance mismatch?

• A. Higher reflection at the interface
• B. Higher refraction
• C. No reflection
• D. Reduced transmission

Answer: (A)

When a wave meets a boundary between two media with a large impedance difference, most of the energy is reflected back into the first medium. The impedance mismatch makes the boundary inefficient at transmitting energy, so the reflection coefficient becomes large in magnitude—approaching unity in extreme cases—and the transmitted portion is greatly reduced. Refraction (a change in direction) can occur, but with a big impedance gap the dominant effect is strong reflection, not no reflection or a focus on refraction. That’s why describing higher reflection at the interface best captures what happens.