Waves & Sound Waves

Waves Defined as a transfer of energy, in the form of a temporary disturbance of a medium, where the medium itself does not move.

Types of Waves Mechanical waves: These are waves that are governed by Newton’s laws. (i.e sound, water). They require a medium. Electromagnetic waves: These are waves that do not require a medium. These types of waves have both a magnetic and electrical component to them. They travel at or near the speed of light.

Wave Oscillation Modes All waves fall into one of three categories: Longitudinal Transverse Torsional This describes how the wave oscillates and hence, how it transmits its energy.

Longitudinal Waves Types of waves where the disturbance is in the same direction as the motion of the wave. (like a spring or sound) The wavelength of a longitudinal wave is defined as the distance between two consecutive compressions or rarefactions. rarefaction compression amplitude

Animated Longitudinal Waves

Transverse Waves Types of waves where the disturbance is perpendicular to the direction of the wave (like water waves and guitar strings). The wavelength is defined as the distance between two consecutive crests or troughs. Or… Twice the length of two consecutive equilibrium points crest amplitude trough

Animated Transverse Waves

Torsional Waves A wave that rotates back and forth along its axis. Tacoma Narrows bridge disaster (Nov. 7, 1940)

The Wave Equations Where: f = frequency (Hz) 1. Cycles = # of complete cycles T = period (time for complete cycle) v = wave speed (m/s)  = wavelength (m) 1. 2. Note: 1 Hertz (Hz) = 1 s-1 OR 1/s 3. lambda

Example #1 A radio wave has a wavelength of 2.887m. What is its frequency? Note, radio waves travel at the speed of light 3.0x108m/s.