If a soundproof door is almost shut but still leaves a small opening, what wave phenomenon is responsible for someone being able to hear sound from the room while standing by the wall to the side of the opening?

Diffraction is the spreading or bending of waves as they pass through an opening or around an edge. Sound passing through the small gap spreads into the area beside the opening, so someone standing by the wall can hear it. The correct choice is diffraction.

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