a) Stationary waves

d) nodes and antinodes

f) the idea that the separation between adjacent nodes (or antinodes) is equal to λ/2, where λ is the wavelength of the progressive wave

stationary wave = a wave produced by two progressive waves

• superposed

• travelling in opposite directions

• of the same frequency, wavelength, and amplitude

node = point of zero displacement on a stationary wave

antinode = point of maximum displacement on a stationary wave

distance between adjacent (anti)nodes = ½λ of the progressive waves = ½λ of the stationary wave