Diffraction angle depends on wavelength relative to gap width

Steps:

• Diffraction occurs when waves bend through a gap, with the angle determined by how the gap size compares to wavelength.
• For significant diffraction, gap width should be similar to or smaller than wavelength; larger gaps reduce bending.
• Wavelength (λ) directly influences spreading: shorter λ means less diffraction.
• Amplitude affects energy but not the geometric angle of diffraction.

Why D is correct:

• Huygens' principle states the diffraction angle θ ≈ arcsin(λ / a), where λ is wavelength and a is gap width, directly linking these factors.

Why the others are wrong:

• A: Amplitude irrelevant to angle; frequency affects λ via v = fλ but isn't independent.
• B: Amplitude doesn't influence diffraction geometry; only gap width with λ matters.
• C: Includes amplitude, which has no effect on the angle despite λ and width being relevant.

Final answer: D