Classify each wave and state the particle motion: (a) ripples on a pond, (b) sound from a drum, (c) light from the Sun, (d) a slinky compressed at one end. Step 1: (a) Ripples: water surface moves up-down while ripples spread outward → transverse. Step 2: (b) Drum sound: air molecules oscillate along the travel direction → longitudinal. Step 3: (c) Sunlight: fields oscillate perpendicular to travel → transverse (also polarisable). Step 4: (d) Slinky push: coils bunch and spread along the slinky → longitudinal. Answer: Transverse: (a), (c). Longitudinal: (b), (d). The test is always: particle motion ⊥ travel = transverse; ∥ travel = longitudinal.