Diffraction depends on wavelength matching obstacle size

Steps:

• Diffraction occurs when waves bend around obstacles comparable to their wavelength.
• A typical doorway is about 1 meter wide.
• Sound waves have audible wavelengths from 0.017 m to 17 m, often matching human-scale openings.
• Electromagnetic waves (UV, visible, X-rays) have wavelengths in nanometers, much smaller than 1 m.

Why A is correct:

• Sound waves diffract noticeably through doorways because their wavelengths (e.g., 1 m for middle C) are comparable to the aperture size, satisfying the diffraction condition where θ ≈ λ/d (λ = wavelength, d = aperture).

Why the others are wrong:

• B: Ultraviolet waves (~10-400 nm) are too short to diffract visibly around a 1 m doorway.
• C: Visible light waves (~400-700 nm) produce negligible diffraction at human scales.
• D: X-rays (~0.01-10 nm) have extremely short wavelengths, preventing observable diffraction.

Final answer: A