Diffraction of waves through a narrow gap

Steps:

• Identify the setup: plane water waves approach a gap between barriers in a ripple tank.
• Apply Huygens' principle: the gap acts as a new wavefront source, producing secondary wavelets.
• Predict pattern: waves diffract, spreading circularly beyond the gap if gap width ≈ wavelength.
• Match to diagrams: select the one showing straight incident waves transitioning to semicircular diffracted waves.

Why B is correct:

• B shows semicircular wavefronts radiating from the gap, aligning with Huygens' principle for diffraction when aperture size matches wavelength.

Why the others are wrong:

• A: Waves continue straight without bending, violating diffraction bending around edges.
• C: Waves converge or refract inward, misrepresenting spreading nature of diffraction.
• D: Waves reflect off barriers without passing through, ignoring transmission through the gap.

Final answer: B