CH 15 & 16

CH 15 & 16WavesSection 1 & 2 ObjectivesExplain how forces cause wavesExplain how waves transfer energyClassify wave typesCalculate a waves speedIdentify properties of waves

The BasicsWaves transfer ENERGY and are caused by FORCES.

PARTS OF A WAVEAMPLITUDE measures the height of each wave crestB. WAVE LENGTH is the distance between 2 crests of a wave, or between 2 troughsC. FREQUENCY is the number of waves that hit an object in a given period of timeD. As frequency increases, WAVE LENGTH decreasesE. CREST is tallest pointF. TROUGH is the lowest pointG. Increase the speed of disturbance, you increase the FREQUENCY. THE WAVEhttp://www.youtube.com/watch?v=-5zmRt4bL8A&safety_mode=true&persist_safety_mode=1&safe=active GRAPHING A WAVEPAGE 499

CALCULATIONSTo find speed of the wave you use the formula SPEED=FREQUENCY X WAVE LENGTHTo find the frequency of waves you DIVIDE NUMBER OF WAVES BY THE TIME IT TOOK TO GET TO A CERTAIN POINTIf the crest of two waves join up exactly, their amplitudes are ADDED

TYPES OF WAVESMECHANICAL WAVES are caused by forces creating a disturbance in a medium.EX)SOUND, WATER, WAVES MADE BY A ROPELONGITUDINAL WAVES Occur when energy travels in the same direction as the disturbanceEX) SOUNDTRANSVERSE WAVES Transfers energy at right angles to the disturbanceEx)WATER WAVES

Types of WavesELECTROMAGNETIC WAVES Are caused by a disturbance that transfers energy through a fieldEX) LIGHT WAVES, MICROWAVES, RADIO WAVES

Section 3 ObjectivesDescribe how waves change as they encounter a barrierExplain what happens when waves enter a new mediumIdentify ways in which waves interact with one another

Reflection1. REFLECTION is the reaction when a waves hits a barrier and cannot pass through itEX) ECHO IN A CANYON EX) IF YOU PUT A SOLID WOOD BARRIER COMPLETELY ACROSS A TANK FULL OF WATER, WAVES IN THE TANK WILL BE REFLECTED BY THE WOOD

REFRACTION2. REFRACTION occurs because waves move through different mediums at different speedsEX)WHEN YOU PUT A STICK INTO A POND AND THE STICK APPEARS TO BE BROKEN

DIFFRACTIONDIFFRACTION is the spreading out of waves through an opening or around the edge of an obstacle.EX)WATER BENDING AROUND A ROCK IN THE RIVER, POND SPREADS OUT PAST A ROCK IN A POND, SHADOW ON THE GROUND

InterferenceWaves interact with one anotherThey can add energy to another waveThey can take energy away from another waveThere are two types of interference: constructive & destructive

InterferenceDestructive interference can cancel another wave outEX) A quiet spot in the classroom during a movie is cause by destructive interferenceConstructive interference occurs when the crests & troughs of tow waves align exactlyEX) When a wave moves across a pond, it transfers water molecules up and down and energy across the pondEX) When a wave passes through the ocean, energy is transferred across great distances while individual areas move up and down

Forces & WaveForces cause waves by creating DISTURBANCESEARTHQUAKES Are caused when forces inside earth cause rocks to move. Earthquake waves are produced and carry kinetic energy through the ground. Roads bent of broken far from the earthquakes center shows that waves TRANSFER ENERGY OVER DISTANCEA moving object has KINETIC ENERGY. It has the most when it is moving the fastest.

Section 1 ObjectivesExplain how sound waves are produced & detectedExplain how sound waves transfer energyDescribe what effects the speed of sound waves

Sound WavesSOUND WAVES Are caused by vibrations. Sound waves transfer energy by PUSHING AIR PARTICLESThe sound of your voice is created by FORCING AIR THROUGH YOUR VOCAL CHORDS MAKING THEM VIBRATE

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Section 3 ObjectivesExplain how the intensity of a wave affects its loudnessDescribe how sound intensity can be controlledExplain how loudness can affect hearingIntensity of Sound (Decibels)The intensity of sound is determined by its amplitude, or the amount of energy carried by a wave.

Intensity of SoundIntensity of SoundSound becomes SOFTER at a distance because the energy of a sound wave is SPREAD OUT OVER A GREATER AREAA CAR MUFFLER & ACCOUSTIC TILES makes sound softer by absorbing energy from sound waves.

AmplificationIncreasing strength of an electrical signalIncreases the intensity of a sound waveSound is converted into vibrations in a coil which is attached to a cone to magnify the sound

AcousticsScientific study of soundHow it is produced and how it is received by humans & animalsThe way waves behave inside a spaceReduce unwanted echoes

SOUND IN A VACUUMROBERT BOYLEPLACE A TICKING CLOCK IN A SEALED JAR AND REMOVED AIR PARTICLESHE HEARD NO TICKING ONCE ALL AIR WAS REMOVEDHE PROVED THAT SOUND DOES NOT TRAVEL THROUGH A VACCUM

Speed of SoundDepends on mediumFaster through liquid than gasesAlso can travel through solid elastic mediums (steel)Sound travels faster through a medium at a higher temperature than a lower one Sound travels slower than light

Section 2 ObjectivesDescribe how the frequency of a wave affects the way it soundsDescribe how sound quality differs from pitchLearn about the Doppler EffectPITCHPitch: HIGHNESS & LOWNESS of a soundTo raise the pitch of a sound, you can INCREASE THE FREQUENCY of the wave. To lower the pitch, you can DECREASE THE FREQUENCY of the wave.

PITCHAs sound passes by, PITCH WILL INCREASEA motorcycles sound is at A HIGHER PITCH when it is coming toward you than going away from you. If you play the same pitch on two different instruments, the notes may sound different because of OVERTONES

Natural FrequencyEvery object has a frequency at which it vibratesEX) piano tunerStrengthening the sound wave is called resonance

Sound QualityTimbreMost sounds are not single waves, but are a combination of wavesThis is why two singers can sing the exact same note, but sound different

Doppler EffectChange in perceived pitch that occurs when the source or the receiver of sound is movinghttp://www.youtube.com/watch?v=Gpe6zIKmoWA&safety_mode=true&persist_safety_mode=1&safe=active

ULTRASOUNDUltrasounds waves are a type of SOUND wave that can be used by bats for locating & avoiding objects,Doctors can use ultrasounds waves to LOCATE AND EXAMINE INTERNAL ORGANS

echolocationSonar

SOUND WAVES CAN DAMAGE HEARING (Page 536) You can damage you hearing by listening to HIGH-INTENSITY SOUNDSYou actually damage the HAIR CELLS of the cochlea.

How musical instruments workPage 541

TelephoneSound waves travel through wires in a telephoneSound waves travel though microwaves in a cell phoneVibrations turn into electrical signalsThe receiver has a diaphragm that helps produce the sound waves

Recorded SoundEdisons phonograph (Page 543)A CD is hard plastic that has millions of microscopic pits arranged in a spiral. The pits contain info that CD players can turn into electrical signals which are then turned into sound waves.