Diffraction maximizes when wavelength equals or exceeds gap width

Steps:

• Diffraction occurs when waves bend around obstacles or through gaps, strongest for long wavelengths relative to gap size.
• For a gap of 8 m, compare each wavelength to this width.
• Greatest diffraction happens when λ ≥ gap width, as waves spread out significantly.
• Thus, λ = 8 m produces the most pronounced bending and spreading.

Why D is correct:

• When wavelength equals gap width (λ = 8 m), diffraction is maximal per Huygens' principle, treating the gap as a secondary wavefront source with minimal interference.

Why the others are wrong:

• A (1 m): λ much smaller than gap, so wave passes straight through with negligible diffraction.
• B (2 m): λ still << gap, resulting in weak bending and near-straight propagation.
• C (4 m): λ half the gap, causing moderate diffraction but less spreading than when λ matches gap.

Final answer: D