Diffraction as Wave Bending

Steps:

• Recall diffraction involves waves bending around obstacles or through openings, not straight-line propagation.
• Examine choices: A describes frequency shift, B node formation, C wave spreading, D wave overlap.
• Match C to standard definition of diffraction in wave optics or acoustics.
• Confirm by eliminating mismatches to other wave phenomena.

Why C is correct:

• Diffraction is defined as the spreading or bending of waves around the edges of an obstacle or aperture, as per Huygens' principle.

Why the others are wrong:

• A: Describes the Doppler effect, involving relative motion.
• B: Refers to standing waves from interference of oppositely traveling waves.
• D: Defines superposition, the general principle when waves meet, not specific to diffraction.

Final answer: C