Elementary School (3-5)
Waves, which are regular patterns of motion, can be made in water by disturbing the surface. When waves move across the surface of deep water, the water goes up and down in place; there is no net motion in the direction of the wave except when the water meets a beach.
Waves of the same type can differ in amplitude (height of the wave) and wavelength (spacing between wave peaks).
Middle School (6-8)
A simple wave has a repeating pattern with a specific wavelength, frequency, and amplitude.
A sound wave needs a medium through which it is transmitted.
High School (9-12)
The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the type of wave and the medium through which it is passing.
Information can be digitized (e.g., a picture stored as the values of an array of pixels); in this form, it can be stored reliably in computer memory and sent over long distances as a series of wave pulses.
[From the 3–5 grade band endpoints] Waves can add or cancel one another as they cross, depending on their relative phase (i.e., relative position of peaks and troughs of the waves), but they emerge unaffected by each other. (Boundary: The discussion at this grade level is qualitative only; it can be based on the fact that two different sounds can pass a location in different directions without getting mixed up.)
Geologists use seismic waves and their reflection at interfaces between
layers to probe structures deep in the planet.