Identifying wave properties from a stationary pattern sketch

Steps:

• Observe the wave sketch: perpendicular displacement indicates transverse wave.
• Measure crest-to-crest distance: pattern shows 40 cm wavelength with fixed nodes and antinodes.
• Note the short time period: pattern remains unchanged, indicating no propagation.
• Confirm type: no compression-rarefaction, ruling out longitudinal.

Why D is correct:

• Stationary waves form standing patterns with fixed nodes (zero amplitude) and antinodes (maximum amplitude), matching the unchanging sketch over time.

Why the others are wrong:

• A: Longitudinal waves involve parallel particle motion, but sketch shows perpendicular displacement.
• B: Wavelength is 40 cm, not 20 cm, based on full cycle distance.
• C: Pattern is fixed, not progressing; progressive waves shift position over time.

Final answer: D