What is diffraction?

• A. Sound waves bending around obstacles.
• B. Sound waves reflecting off surfaces.
• C. Sound waves changing speed when entering a different medium.
• D. Sound waves increasing in frequency.

Answer: (A)

Diffraction is the bending and spreading of waves as they meet an obstacle or pass through a gap. For sound, this means the waves bend around edges and spread into the space beyond barriers, so you can hear sounds even when you aren’t in a direct line with the source. This is why you can hear someone around a corner or through a doorway. It’s different from reflection, where waves bounce off surfaces; and from refraction, where waves change speed and bend when moving into a different medium. It isn’t about a change in frequency, which relates to pitch changes due to motion rather than bending around obstacles. So describing sound waves bending around obstacles best captures diffraction.