Diffraction: Waves bending through a narrow gap

Steps:

• Identify diffraction as wave spreading after passing through an opening comparable to wavelength.
• Look for diagram showing straight waves entering a gap and emerging as curved, circular wavefronts.
• Eliminate options with reflection (bouncing back) or refraction (bending in medium change).
• Confirm the pattern matches Huygens' principle, where each wave point acts as a source.

Why C is correct:

• It depicts waves diffracting through a slit, producing semicircular wavefronts beyond the gap, per Huygens' principle.

Why the others are wrong:

• A shows reflection, with waves bouncing off a barrier.
• B illustrates refraction, with waves bending due to depth change.
• D represents interference, with overlapping wave patterns forming nodes and antinodes.

Final answer: C