WAVESDefinition:

A traveling disturbance that carries energy through matter and space

Waves transfer energy without transferring matter.Waves are produced by something that vibrates.

WAVESVibrations:

Movement that follows the same path, repeatedlyMost waves are caused by a vibrating object.

WAVESMechanical Waves:

Waves that require a mediumTwo types: transverse and compression

(longitudinal)Examples are seismic and sound waves.Medium: matter (the stuff) through which a

wave travelsExamples include water, air, and solids.

TYPES OF WAVESTRANSVERSE

•Movement of the medium is perpendicular to the propagation of the wave.•Examples – electromagnetic waves, waves on a rope, water waves•Draw an example in your notes. (Think of the slinky.)

COMPRESSION(LONGITUDINAL)

•Particles in a medium vibrate parallel to the propagation of wave motion.•Example – sound waves•Draw an example in your notes. (Think of the slinky.)

Parts of a WaveCrest: high point of the wave formTrough: low point of the wave formCompression: more dense region of a

longitudinal waveRarefaction: less dense region of a longitudinal

wavecrest

trough

Rest position

Wave PropertiesWavelength:Defined - distance between one point on a wave and the nearest point just like it Distance from…

1) Crest to crest2) Trough to trough3) Start of one compression to the next4) Start of one rarefaction to the next

Rest position

wavelength

wavelength

wavelength

wavelength

Wave PropertiesFrequency:Defined - The number of wavelengths (or number of

vibrations) that pass a fixed point each second

Frequency is expressed in hertz (Hz).A frequency of 1 Hz means that one wavelength

(or one vibration) passes by in one second. Two vibrations per second is 2 Hz.

In SI units, 1 Hz is the same as 1/s.

Wave Properties

Period:Defined - the amount of time it takes one

wavelength to pass a point, measured in seconds

T = 1/f

As the frequency of a wave increases, the period decreases.

Wave Properties

Wavelength and Frequency:

The relationship is inversely proportional:

Wavelength (λ)

Frequency (f)

Wavelength (λ)

Frequency (f)

Wave PropertiesWave Speed:

Depends on… the medium it is traveling through.

Sound waves travel faster in liquids and solids than they do in gases. However, light waves travel more slowly in liquids and solids than they do in gases or in empty space.

Sound waves travel faster in material when the temperature of the material is increased.

Wave Speed (continued):

Calculated by multiplying its frequency times its wavelength

speed (in m/s) = frequency (in Hz) x wavelength (in m)

v = ƒ λ (m/s)ƒ = v / λ (Hz)

λ = v / ƒ (m)

Wave Properties

Wave Properties

Amplitude and Energy:

Amplitude is related to the energy transferred by a wave.

The greater the wave’s amplitude, the more energy the wave transfers.

Wave Properties

amplitude

amplitude

λ

λ

crest

trough

Reflection When a wave comes to the end of the medium it

is traveling in, it is partially reflected back.

Types of Mirrors

Plane

Convex

Concave

Refraction

When a wave crosses a boundary between mediums and its velocity changes as a result, the transmitted wave may move in a different direction than the incident wave (“bent”).

Snell’s LawSin(θ)1 n1 = Sin(θ)2 n2

n – index of refraction

nair = 1.00 Θ = 30°

nwater = 1.33

DiffractionProcess of waves bending around obstacles

InterferenceWhen 2 waves pass through the same region of

space at the same time. The resultant displacement is always the sum of the separate (component) displacements.

Constructive Interference:Add Together

Destructive Interference: Cancel Each Other Out

Constructive vs. Destructive

Two waves in phase Two waves 180° our of phase

Combined

waveform

Wave 1

Wave 2