x y A λ (wavelength) N N Crest (+A) Trough (−A) y = A sin(kx − ωt) λ/2

Key observations:

• Crest (maximum displacement +A) and trough (−A) separated by λ/2
• Nodes (zero crossing) separated by λ/2 in a standing wave
• Wave number k = 2π/λ; angular frequency ω = 2πf
• Progressive wave equation: y = A sin(kx − ωt) for rightward travel