Lesson Plan

Describe superposition as the combination of waves and explain that waves superimpose by adding their disturbances

Distinguish constructive interference from destructive interference and predict the resultant amplitude in the pure cases

Describe a standing wave and identify its nodes and antinodes

Distinguish reflection (including inversion at a fixed end) from refraction of waves

13.3

"Most waves appear complex because they result from two or more simple waves that combine as they come together at the same place at the same time—a phenomenon called superposition." "Waves superimpose by adding their disturbances; each disturbance corresponds to a force, and all the forces add. If the disturbances are along the same line, then the resulting wave is a simple addition of the disturbances of the individual waves, that is, their amplitudes add." "Because the disturbances add, the pure constructive interference of two waves with the same amplitude produces a wave that has twice the amplitude of the two individual waves, but has the same wavelength." "Such waves are called standing waves and are formed by the superposition of two or more waves moving in opposite directions. ... The nodes are the points where the string does not move ... The antinode is the location of maximum amplitude in standing waves." "As it is reflected, the wave experiences an inversion, which means that it flips vertically. ... At the boundary between media, waves experience refraction—they change their path of propagation. As the wave bends, it also changes its speed and wavelength upon entering the new medium."