Diffraction angle depends on wavelength and gap width

Steps:

• Diffraction occurs when waves bend through a gap comparable to their wavelength.
• The angle of diffraction θ satisfies sinθ ≈ λ/d for small angles, where λ is wavelength and d is gap width.
• Amplitude influences wave intensity but not spreading angle.
• Frequency affects λ via λ = v/f (v fixed in ripple tank), so λ is the direct factor.

Why D is correct:

• The diffraction formula sinθ = mλ/d (m=1 for first minimum) shows θ depends directly on λ and d.

Why the others are wrong:

• A: Amplitude irrelevant; frequency alters λ indirectly but isn't the key factor.
• B: Amplitude does not affect diffraction angle.
• C: Amplitude irrelevant to angle; only gap width matters among these.

Final answer: D