Chapter 14Chapter 14

WavesWaves

Wave a repeating disturbance or movement that transfers

energy through matter or space A rhythmic disturbance that carries energy through

matter or space. Molecules pass energy on to neighboring molecules

Waves carry energy without transporting matter All waves are produced by something that vibrates Medium - material which a wave travels thru

May be solid, liquid, or gas Not all waves need a medium to travel through

Example: Light waves

Wave Pulse A single bump or disturbance that travels through a

medium

Mechanical wavesMechanical waves waves that can travel only through matterwaves that can travel only through matter

Transverse waveTransverse wavess matter in the medium moves back and forth at right matter in the medium moves back and forth at right

angles to the direction that the wave travels.angles to the direction that the wave travels. Example: Water wavesExample: Water waves

Longitudinal or Compressional waveLongitudinal or Compressional wavess matter in the medium moves in the same direction matter in the medium moves in the same direction

that the wave travels.that the wave travels. Example: Sound wavesExample: Sound waves

Surface WavesSurface Waves Combination of both transverse or compressionalCombination of both transverse or compressional

examples: water waves, seismic wavesexamples: water waves, seismic waves

Ways waves differ1. How much energy they carry2. How fast they travel3. How they look

Transverse waves have crests & troughsCrest —the highest pointsTroughs—the lowest points.

CompressionsDense regions of compressional waves

RarefactionsLess dense regions of compressional waves

Wavelength (Wavelength (λλ))the distance between one point in the the distance between one point in the

wave and the nearest point just like itwave and the nearest point just like itFrequencFrequency (f)y (f)

how many wavelengths pass a fixed how many wavelengths pass a fixed point each secondpoint each secondExpressed in hertz (Hz)Expressed in hertz (Hz)

As frequency increases, wavelength As frequency increases, wavelength decreases.decreases.

The frequency of a wave equals the rate The frequency of a wave equals the rate of vibration of the source that creates it.of vibration of the source that creates it.

Wave velocity, vdescribes how fast wave moves forward

velocity = wavelength * frequencySpeed of a wave = v = λ*ff = 1/T = 1/period

Light waves travel faster than sound waves

Sound waves travel faster in liquids and solids than in gas

Light waves travel faster in gases and empty space than in liquids & solids

AmplitudAmplitudee a measure of the energy in a wavea measure of the energy in a wave

More energy a wave carries, the greater its amplitude.More energy a wave carries, the greater its amplitude.

Amplitude of compressional waves is related to Amplitude of compressional waves is related to how tightly the medium is pushed together at how tightly the medium is pushed together at the compressionthe compression The denser the compressions, the larger the The denser the compressions, the larger the

amplitude is and the more energy the wave carriesamplitude is and the more energy the wave carries The less dense the rarefactions, the larger the The less dense the rarefactions, the larger the

amplitude and the more energy the wave carriesamplitude and the more energy the wave carries Amplitude of transverse wavesAmplitude of transverse waves

The distance from the crest or trough of a wave to The distance from the crest or trough of a wave to the normal position of the mediumthe normal position of the medium Ex. how high ocean wave appears above water levelEx. how high ocean wave appears above water level

Reflection occurs when a wave Reflection occurs when a wave strikes an object and bounces off strikes an object and bounces off of it.of it.All types of waves can be reflected.All types of waves can be reflected.The angle of incidence always The angle of incidence always

equals the angle of reflectionequals the angle of reflectionNormalNormal

An imaginary line that is An imaginary line that is perpendicular to reflective surfaceperpendicular to reflective surface

Incidence WaveIncidence Wave The wave that strikes the boundaryThe wave that strikes the boundary

Angle of incidenceAngle of incidence the angle formed by the wave striking the the angle formed by the wave striking the

surface and the normalsurface and the normal Angle of reflectionAngle of reflection

angle formed by reflected wave and normalangle formed by reflected wave and normal RefractioRefractionn

bending of a wave caused by a change in its bending of a wave caused by a change in its speed as it moves from 1 medium to anotherspeed as it moves from 1 medium to another

The greater the change in speed is, the more The greater the change in speed is, the more the wave bends.the wave bends. When a wave passes into a material that slows it When a wave passes into a material that slows it

down, the wave is bent toward the normal.down, the wave is bent toward the normal. When a wave passes into a material that speeds it When a wave passes into a material that speeds it

up, the wave is bent away from the normal.up, the wave is bent away from the normal. DiffractioDiffractionn

an object causes a wave to change direction and an object causes a wave to change direction and bend around itbend around it If obstacle is smaller than wavelength, wave diffracts a lotIf obstacle is smaller than wavelength, wave diffracts a lot If obstacle is larger than wavelength, wave does not If obstacle is larger than wavelength, wave does not

diffract muchdiffract much

The larger the obstacle is compared to the The larger the obstacle is compared to the wavelength, the less the waves will diffractwavelength, the less the waves will diffract

InterferencInterferencee ability of two or more waves to combine & ability of two or more waves to combine &

form a new waveform a new wave Waves pass thru each other & continue in Waves pass thru each other & continue in

original directionoriginal direction New wave exists only while original waves New wave exists only while original waves

are overlappingare overlapping Constructive interferenceConstructive interference

waves add togetherwaves add together Destructive interferenceDestructive interference

waves subtract from each otherwaves subtract from each other

Standing waveStanding wavess a wave pattern that stays in one placea wave pattern that stays in one place Form when waves of equal wavelength & Form when waves of equal wavelength &

amplitude that are traveling in opposite amplitude that are traveling in opposite directions continuously interfere with each directions continuously interfere with each otherother

NodesNodes the places where two waves always cancel the places where two waves always cancel

each othereach other ResonanceResonance

ability of an object to vibrate by absorbing ability of an object to vibrate by absorbing energy at its natural frequencyenergy at its natural frequency