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Physics

Wave Reflection

Quick fact

A wave reflecting from a fixed (rigid) boundary inverts its phase—the reflected wave is flipped upside down—while reflection from a free (flexible) boundary preserves the original phase. This is easy to observe with a rope or slinky.

Why this is interesting

Have you ever wondered why you see your reflection in a calm lake, or why a shout echoes back from a distant cliff? These everyday experiences are both caused by the same simple but powerful phenomenon: wave reflection.