Demonstrating wave diffraction visually

Steps:

• Define diffraction as the bending and spreading of waves around obstacles or through openings.
• Evaluate apparatus for clear visualization of wave behavior in a classroom setting.
• Identify ripple tank as ideal for producing and observing 2D water waves passing through slits or around barriers.
• Eliminate options that primarily show wave propagation without easy diffraction demonstration.

Why B is correct:

• Ripple tank allows direct observation of water waves diffracting through narrow gaps, aligning with Huygens' principle where each wave point acts as a source of secondary waves.

Why the others are wrong:

• A. Long spring demonstrates longitudinal waves or pulses but lacks visual spreading around edges.
• C. Rope shows transverse wave pulses or standing waves, not clear diffraction bending.
• D. Stretched string is used for transverse waves like harmonics, with diffraction not easily observable.

Final answer: B