# The Natu re and Behavior o f Chapter

The Natu re and Behavior o f Chapter 1 Waves Wav0: e

s Learning Goals 0 Compare and contrast transverse and compressional waves. 0 Identify the parts of a wave.

What is a Wave? 0 Wave: a repeating disturbance or movement that transfers energy through matter or space 0 Molecules pass their energy on to neighboring molecules

What is a Wave? 0 Waves carry energy WITHOUT transporting matter 0 All waves are produced by something that vibrates

0 Examples: sound, light Waves and Energy 0 Think of a pebble falling into a pool of water and ripples forming.

0 The pebble has energy because it is falling. Waves and Energy 0 When the pebble

splashes into the pool it transfers its energy to the nearby water. 0 The energy is then transferred from water molecule to water molecule.

Waves and Matter 0 Think about a boat on a lake. 0 The waves bump the boat but they dont carry the boat along with it as they pass. 0 The waves dont even carry the water

they just carry the energy forward. Mediums 0 Medium: a material through which a wave travels 0 Can be solids, liquids, or gases

0Waves that can only travel through mediums are called mechanical waves Mediums 0 Not all waves need a medium 0Example: light and radio waves can travel

through space Mechanical Waves 0 Mechanical waves: waves that can travel only through matter 0 There are two main types of

mechanical waves: 0 Transverse 0 Compressional Transverse Waves 0 Transverse waves: matter in the

medium moves back and forth at right angles to the directions that the wave travels 0 Example: water waves Compressional Waves

0 Compressional waves: matter in the medium moves in the same direction that the wave travels 0 Example: sound waves Combinations 0 Some waves are a mixture of

transverse and compressional waves. 0 An example is seismic waves, which move the Earth up and down and side to side.

Propertie s of Waves Chapter 1 0: Waves The Parts of a Wave 0 Waves can differ in how much

energy they carry and in how fast they travel. 0 Waves also have other characteristics that make them different from each other.

The Parts of a Wave 0 A transverse wave has alternating high points called crests and low points called

troughs. The Parts of a Wave 0 When you make compressional waves in a coiled spring, a compression is a region where the coils are close together.

The Parts of a Wave 0 The coils in the region next to a compression are spread apart, or less dense. This less-dense region of a compressional wave is called a rarefaction.

Wavelength 0 A wavelength is the distance between one point on a wave and the nearest point just like it. Wavelength

0 For transverse waves the wavelength is the distance from crest to crest or trough to trough. Wavelength 0 A wavelength in a

compressional wave is the distance between two neighboring compressions or two neighboring rarefactions.

Frequency 0 The frequency of a wave is the number of wavelengths that pass a fixed point each second. 0 Frequency is expressed in hertz (Hz).

Wavelength and Frequency 0 As frequency increases, wavelength decreases. 0 The frequency of a wave is always equal to the rate of vibration of the

source that creates it. Wavelength and Frequency 0 If you move the rope up, down, and back up in 1 s, the frequency

of the wave you generate is 1 Hz. Wavelength and Frequency 0 The speed of a wave depends on the medium it is traveling through. 0 Sound waves usually travel faster in

liquids and solids than they do in gases. 0 However, light waves travel more slowly in liquid and solids than they do in gases or in empty space. Wavelength and

Frequency 0 Sound waves usually travel faster in a material if the temperature of the material is increased. Calculating Wave Speed 0 You can calculate the speed of a

wave represented by v by multiplying its frequency times its wavelength. v= speed (m/s) f= frequency (Hz)

Practice 0 What is the speed of a wave that has a frequency of 3 Hz and a wavelength of 2 meters? Practice 0 What is the frequency of a wave

that has a wavelength of 20 m and a speed of 5 m/s? Practice 0 What is the wavelength of a wave that has a frequency of 200 Hz and

a speed of 350 m/s? Amplitude and Energy 0 Amplitude, or a waves height, is related to the energy carried by a wave. 0 The greater the waves amplitude is,

the more energy the wave carries. 0 Amplitude is measured differently for compressional and transverse waves. Amplitude and Energy 0 Compressional Waves: 0 The amplitude of a compressional

wave is related to how tightly the medium is pushed together at the compressions. Amplitude and Energy 0 The denser the medium is at the

compressions, the larger its amplitude is and the more energy the wave carries. 0 The closer the coils are in a compression, the farther apart they are in a rarefaction.

Amplitude and Energy 0 So the less dense the medium is at the rarefactions, the more energy the wave carries. More dense

Less dense Amplitude and Energy 0 Transverse Waves: 0 The amplitude of any transverse wave is the distance from the crest or trough of the wave to the rest position of the

medium.

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