WavesUnit 4

- sound in air- AC electricity in a wire- an earthquake in rock- ocean waves in waterradio waves- light - infrared radiation - X-rays - gamma rays- microwaves - - UV (ultraviolet)

Key Points:1. Learn the characteristics of Transverse andlongitudinal Waves.2. Understand how waves are created andpropagated.3. Understand the properties of waves.

Definition of A Wave

phenomenon by which energy propagates through a distance as a result of vibrational motions

Types of Waves With Respect to Medium:

Electromagnetic: these waves do not require a medium in which to travel. Light is an example of this. You will study these in Physics 30.

Mechanical: these waves do require a medium in which to propagate.

Types of Waves With Respect to

Vibrational Direction:

Longitudinal waves: the particles of the medium vibrate parallel to the direction of energy travel (cannot be polarized)

Transverse waves: the particles of the medium vibrate perpendicularly to the direction of energy travel, (can be polarized)

Diagram of a longitudinal wave: particle displacement is parallel to the

direction of wave propagation.

ENERGY

WAVEEqual Spacing

Longitudinal Terminology: Compression: is the

region of higher concentration of the medium compared to the mean position.

Rarefaction: is the region of lower concentration of the medium compared to the mean position.

Node: a stationary point in a vibratory body where the amplitude is zero.*** Everything that can be said about a longitudinal wave can also be said about a transverse wave with polarization being the only exception.

Longitudinal Waves

Diagrams of Compression and Rarefaction

Diagram of a Transverse Wave particle displacement is perpendicular to

the direction of wave propagation.

Lab

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d Tra

nsvers

e

Wave

Node

Energy

Polarization of Transverse Wave

Transverse Terminology:

Amplitude: the maximum displacement of the medium from the mean or zero position.

Pulse: a single displacement of the medium

Cycle: a repetition in the wave.

Crest: the maximum positive displacement from the mean position

Trough: the maximum negative displacement from the mean position. Opposite side of the crest.

Other Terminology

Wavelength: it is the lateral displacement traveled during one cycle. (λ)

Frequency: the number of cycles per unit time (Hz)

Period: the time it takes to complete one cycle (s)

Node: A stationary point in a vibratory body where the amplitude is zero.

The period and frequency of a wave are related by the equation 1f

T

Waves and SHMWaves are an example of SHM because they repeat

over and over just like a mass on a spring or a pendulum. As shown below, a mass on a spring makes a sinusoidal wave pattern as it oscillates.

The Wave Equation The universal wave

equation links the velocity of a wave, the wavelength and the frequency of a wave in the following manner. Velocity depends upon the medium through which the wave is traveling.

Velocity is constant for a given medium so:

v f

Examples: Example 1 : A wave has a velocity of

70 .0 m/s and its frequency is 10.0 Hz. What is the wavelength?

Example 2: A wavelength of a wave is 2.00 m and its velocity is 300 cm/s. Calculate its frequency and period.

Assignment: Read Textbook Pages 392-410 Do Workbook p. 280 #5, 6, 9, 16, 17,

18 Handout #1 - 7