All waves are traveling disturbances which carry energy from place to place.

Transverse waves the disturbance is perpendicular to the direction of travel of the wave.

Longitudinal waves the disturbance is parallel to the direction of travel of the wave.

Periodic waves have repeating patterns. One cycle is one complete motion of a particle.

The amplitude is the maximum displacement of a particle from the rest position.

The wavelength λ is the horizontal length of one cycle.

The period T is the time required for one complete cycle.

The frequency f is the number of cycles per one second.

Frequency and period are reciprocals. f = 1/ T v = λ / T = f λ

Ex 1 - An AM station broadcasts at a frequency of 1230 kHz and an FM station broadcasts at 91.9 mHz. What are the wavelengths of these two stations?

The compressed area in a longitudinal wave is called a compression. The area where particles are further apart is called a rarefaction.

A sound with a single frequency is a pure tone. Most healthy people hear in a range of 20 Hz to Hz (20 kHz).

Frequencies below 20 Hz are infrasonic, those above 20 kHz are ultrasonic.

Our brain interprets frequency as pitch.

When sound travels through a long, slender solid bar, the speed v is: v = √ Y/ρ Y is Young’s Modulus and ρ is density.

The power of a sound wave is measured in watts W. The intensity I of a wave is the power per unit area, W/ m 2.

Ex x W of sound power passes perpendicularly through two surfaces; one of area 4.0 m 2 and the other of area 12 m 2. Find each sound intensity.

W/m 2 is the threshold of hearing. (for humans)

For spherically uniform radiation of sound: I = P/ 4πr 2.

The intensity level β(in decibels) is defined as follows: β = 10 log(I/I 0 )

0 decibels means the sound intensity is at the threshold of human hearing, not that the intensity is zero.

Doppler Effect - apparent change in pitch when a sound maker or listener are moving with respect to each other.

Source moving toward stationary listener: f’ = f[ 1/(1 - v s /v)] Source moving away from stationary listener: f’ = f[ 1/(1 + v s /v)]

listener moving toward stationary source: f’ = f(1 + v O /v) listener moving away from stationary source: f’ = f(1 - v O /v)

Chapter 17 The Principle of Linear Superposition - When two or more waves are present at the same time at the same place, the resultant wave is the sum of the individual waves.

When waves are in phase they produce constructive interference. When they are out of phase they produce destructive interference.

Diffraction is the bending of a wave around an obstruction or the edges of an opening.

When tones of two different frequencies are produced beats are heard where constructive interference takes place.

The beat frequency is the difference between the two frequencies.

In a transverse standing wave pattern, the nodes are places that do not vibrate at all, and antinodes vibrate with maximum amplitude.

The distance between two successive nodes in a standing wave pattern is one-half a wavelength.

Integer multiples of a frequency are harmonics and frequencies above the fundamental are overtones.