Waves 23.3 – Wave Motion pp. 567- 571

23.3 Wave Motion A wave front is the leading edge of a moving wave which is considered to be the crest for purposes of modeling. The crests of a plane wave look like parallel lines. The crests of a circular wave are circles.

23.3 Four wave interactions When a wave encounters a surface, four interactions can occur: reflection, refraction, diffraction, or absorption.

23.3 Wave interactions A boundary is an edge or surface where things change. Reflection, refraction, and diffraction usually occur at boundaries.

REFRACTION The bending of a wave as it passes at an angle from one medium to another is called refraction. The speed of a wave changes depending on the medium in which it is traveling

23.3 Wave interactions Diffraction usually changes the direction and shape of the wave. When a plane wave passes through a small hole diffraction turns it into a circular wave.

23.3 Wave interactions Absorption is what happens when the amplitude of a wave gets smaller and smaller as it passes through a material. The wave energy is transferred to the absorbing material. Curtains in theaters absorb backstage sounds so the audience doesn’t hear them.

23.3 Transverse waves The oscillations of a transverse wave are not in the direction the wave moves. They are perpendicular to the direction of the wave movement.

23.3 Longitudinal waves The oscillations of a longitudinal wave are in the same direction that the wave moves.

23.3 Constructive interference Constructive interference happens when waves add up to make a larger amplitude. Suppose you make two wave pulses on a stretched string. One comes from the left and the other comes from the right. When the waves meet, they combine to make a single large pulse.

23.3 Destructive interference What happens when one pulse is on top of the string and the other is on the bottom? When the pulses meet in the middle, they cancel each other out. During destructive interference, waves add up to make a wave with smaller or zero amplitude.