WavesWavesWhere They Come From and Where They Come From and Where They Are Going Where They Are Going

What Are Waves? What Are Waves? • WavesWaves: any disturbance that transfers : any disturbance that transfers

energy through matter or space energy through matter or space

Energy can be carried away from Energy can be carried away from its source by a wave…but the its source by a wave…but the material that the wave moves material that the wave moves through does not movethrough does not move

ExampleExample: sounds moves through air, but : sounds moves through air, but the air does not movethe air does not move

Wave EnergyWave Energy• Some waves transfer energy by Some waves transfer energy by

vibration of particles in an objectvibration of particles in an object

MediumMedium: substance in which waves can flow: substance in which waves can flow

** Can be a ** Can be a solid, liquid or solid, liquid or

a gasa gas

Types Of WavesTypes Of Waves• 2 Types2 Types

1. Transverse Waves1. Transverse Waves

2. Longitudinal Waves2. Longitudinal Waves

These two waves can be identified by the These two waves can be identified by the direction in which the particles of the direction in which the particles of the

medium vibrate compared with the medium vibrate compared with the direction in which the waves traveldirection in which the waves travel

Transverse WavesTransverse Waves• TransverseTransverse: waves that move across: waves that move across

Particles in a Particles in a transverse wave transverse wave move across or move across or perpendicular to perpendicular to the direction of the direction of the wavethe wave

Longitudinal WavesLongitudinal Waves• LongitudinalLongitudinal: the particles of a medium : the particles of a medium

vibrate back and forth along the path that vibrate back and forth along the path that the wave travelsthe wave travels

Properties of WavesProperties of Waves• AmplitudeAmplitude: the maximum distance the : the maximum distance the

wave vibrates from its rest positionwave vibrates from its rest position

Larger the amplitude = taller waveLarger the amplitude = taller wave

What Does Amplitude Mean? What Does Amplitude Mean? • Small AmplitudeSmall Amplitude = low energy = low energy

• Large AmplitudeLarge Amplitude = high energy = high energy

What Happens When Waves Run Into What Happens When Waves Run Into Each Other?Each Other?

• Wave InterferenceWave Interference: occurs when : occurs when two or more waves overlaptwo or more waves overlap

1. Constructive Interference1. Constructive Interference

2. Destructive Interference2. Destructive Interference

Constructive InterferenceConstructive Interference

As the waves come together, the As the waves come together, the individual amplitudes of the waves, individual amplitudes of the waves,

combine to “construct” a newer, larger combine to “construct” a newer, larger wavewave

Destructive InterferenceDestructive Interference

As the waves come together, the As the waves come together, the individual amplitudes of the waves, individual amplitudes of the waves, cancel each other to “deconstruct” a cancel each other to “deconstruct” a

wavewave

WavelengthWavelength• WavelengthWavelength: the distance between any : the distance between any

two adjacent crests or compressionstwo adjacent crests or compressions

FrequencyFrequency• FrequencyFrequency: the number of waves : the number of waves

produced in a given amount of time produced in a given amount of time

Expressed in Expressed in HertzHertz

Wave SpeedWave Speed• Wave SpeedWave Speed: the speed at which a : the speed at which a

wave travelswave travelsv = λ x fv = λ x f

Expressed in m/sExpressed in m/s

V = velocity of V = velocity of wavewaveλ = wavelength λ = wavelength

f = frequency (Hz)f = frequency (Hz)