Traveling waves 20.1 The wave Model

Goal To understand the properties and characteristics that are common to waves of all types.

The Wave Model We will explore the basic properties of waves with a wave model, emphasizing those aspects of wave behavior common to all waves. The wave model is built around the idea of a traveling wave. A traveling wave is an organized disturbance traveling with a well-defined wave speed.

Two wave motions Two types of traveling waves Transverse wave ◦ Up and down movement ◦ Displacement is perpendicular to the direction in which the wave travels. ◦ Electromagnetic waves are transverse waves.

Second type Longitudinal wave ◦ The particles move parallel to the direction in which the wave travels. ◦ Sound waves ◦ Think of the oscillating loudspeaker.

Waves that have both Other waves have characteristics of both transverse and longitudinal waves. Water waves Surface moves up and down Individual water molecules actually move both perpendicular and parallel to the direction of the wave.

Classifying waves based on medium Mechanical waves ◦ Needs a medium such as air or water ◦ Sound and water waves Electromagnetic waves ◦ Self-sustaining oscillations ◦ Require no material medium ◦ Can travel through vacuum Matter waves ◦ Discovered in 20 th century- basis of quantum physics. ◦ Electrons and atoms have wave-like characteristics.

medium The medium of a mechanical wave is the substance through or along which the waves moves. Must be elastic That is, a restoring force of some sort brings the medium back to equilibrium after is has been displaced. A wave displaces the atoms from equilibrium when it moves through the medium. This is called a disturbance. The disturbance of a wave is an organized motion of the particles in the medium.