Diffraction improves when wavelength exceeds gap width

Steps:

• Diffraction occurs when waves bend around obstacles or through gaps, most noticeable if wavelength is comparable to or larger than gap size.
• For better demonstration, maximize bending and spreading; this requires longer wavelengths relative to the fixed gap.
• Increasing wavelength directly makes waves diffract more prominently without altering other factors.
• Evaluate options: amplitude affects energy, not bending; frequency inversely affects wavelength; gap width changes the obstacle scale.

Why C is correct:

• Diffraction is significant when λ ≥ gap width (wave nature principle), so increasing wavelength enhances observable spreading.

Why the others are wrong:

• A: Amplitude changes wave height but not diffraction pattern.
• B: Higher frequency shortens wavelength (v = fλ, v constant), reducing diffraction.
• D: Wider gap allows straighter passage, minimizing bending.

Final answer: C