Indezine Template

Waves, Sound and LightWave PropertiesWhat is a wave?Disturbance or vibration that transmits energy but not matterExamplesSound, light, radiowaves, earthquakes

Types of WavesMechanical Waves- Use a mediumTransverse waves- particles move perpendicular to wave motionLongitudinal Waves- particles move parallel to wave motion

A longitudinal wave example is when you compress or stretch the spring. Remember a wave is motion of energy.

A medium is substance the wave is transported in.3Parts Of A WaveCrest-top of the waveTrough- Bottom of the waveAmplitude (A)-height from resting positionWavelength ()- distance travelled by a single wave

On a longintunal Wave- crests- compressed regions troughs- stretched regions wavelength is still crest to crest or trough to trough4Frequency and Period Period (T)- time for one complete cycle or wavelength (in s)Frequency (f)- number of waves per second (Hertz, Hz)Hertz=1/s or s-1Frequency and period are reciprocals of themselvesf= 1/T T= 1/fThey are inverselyproportional

ExamplePlaying middle C on a piano produces a sound with a frequency of 256 Hz. What is the period of the sound wave?f= 256 HzT=?T=1/fT=1/256T=0.004 sA hertz is 1/s, so when you take the reciprocal of frequency the unit is converted into seconds6Speed of WavesRemember V=d/tSo to get speed we need distance and timeA single waveDistance travelled is one wavelength, Time is one period, TVelocity of a wave=wavelength x frequencyv=fRemember f=1/T 7Example An air horn sound at a frequency of 220 Hz. If the speed of sound in air is 330 m/s, what is the wavelength of the sound wave?1.5 m8ExampleThe distance between successive crest in a series of water is 4.0 m, and the crests travel 8.6 m in 5.0 seconds. Calculate the frequency of a block of wood bobbing up and down on these water waves.= 4.0 md=8.6 mt=5.0 sf=?V=fV=d/tV= 8.6/5 V=1.72 m/s 1.72=4ff= 0.43 hz9WavesInterferenceInterference Two different material objects can not occupy the same space at the same timeWaves are not matter but they can displace matterWaves can occupy the same place at the same timeWhen waves overlap it is called superposition

Constructive Interference Two waves superimposing that are on the same side of equilibriumThey will enhance each other or add up

Same side of equilibrium- they are both on the topIn the first and last image- notice that after they superimpose they return to their original state12Destructive Interference Waves are on opposite sides of equilibriumThey will weaken each other or subtract

Standing WavesA wave that remains in constant positionCan occur when a medium is moving in the opposite direction or when two waves interfere with each other, or constructive and destructive interference

Reflection From a BoundaryWhen waves hit a boundary the wave will be reflectedIf the boundary is fixed the wave will be reflected AND INVERTEDIf the boundary is free the wave will just be reflected

A free boundary- a rope that is loosely tied to a pole, it is able to rotate15Standing WavesIf a series of waves are sent along a string the reflected pulse will interfere with itselfIf the waves are sent at just the right frequency we will create a standing waveMaximum Wavelength on a standing wave is 2L

Both ends have to be nodesThe possible wavelengths here are 2L (b) This is only of a wave so the wavelength is twice the length of the string, L (c) this is a full wave and the length of the string is equal to one wavelength, and 2/3L (d) this is 1 and waves, so the wavelength is 2/3 the length of the string16Antinodes and NodesAreas of complete destructive interference have NO amplitude are nodesAreas of complete constructive interference have LARGE amplitudes are antinodes

WavesSoundSoundBegins with a vibrating objectIs a longitudinal waveThe compression is where density and pressure are at a maximum (crest)The rarefaction is the region are the minimum points (trough)

Sound CharacteristicsNeeds a medium to travelThe higher the temperature the fasterHigher temp=more energy=more vibrationsThe more dense the faster Vibrations will occur more quickly if the molecules are closer togetherPitch is determined by frequencyVolume is determined by amplitude

Clicker QuestionWhich statement is true?A) If a tree fell in outer space no one can hear it B) A dog whistle has produces sounds that have a high amplitudeC) If you are at a concert all of the sound waves have a high frequencyD) Sound travels faster in air than water

A Sound can not travel in a vacuum or space! It needs a mediumB- pitch= high frequencyC- Loud=high amplitudeD- water=denser so the sound waves travel faster21Clicker questionWhich medium would have faster sound waves?A) Gas (at 0 degrees)B) Liquid (at 0 degrees)C) Solid (at 0 degrees)

C22Minimum and Maximum FrequencyFrequency pertains to pitch not loudnessMinimum- 20 HertzBelow- infrasonic wavesMaximum- 20,000 Hertz Above-ultrasonic waves

What are the corresponding wavelengths if the speed of sound in air is 343 m/s?23The Doppler EffectWhen there is movement involved there is an observed change in frequencyThis can be seen with all types of waves

Imagine a bug bouncing up and down on the water, now imagine that bug skimming along the surface of the pond. The waves in back have a longer wavelength and a lower f, the waves in front have a shorter wavelength and a higher frequency24The Doppler EffectYou hear a high pitch as an ambulance approaches you and as soon as it passes the pitch decreases suddenlyCompared to the noise being right beside youIt has a higher pitch as it approaches youIt is a lower pitch when it moves away from you

Radar guns work with the doppler effect too.The radar hits the 25The Red ShiftRed light has the longest wavelength (colors)When we look at other galaxies we notice that their colors are shifted towards redThis is due to the Doppler effectWhat does this indicate?The universe is expanding

Speed of a radar gun can be estimated by measuring the difference in frequency between emitted and reflected radar waves26ResonanceObjects/Substances can have a natural frequency in which it will begin to vibrate when that frequency strikes the objectIf another object begins emitting that wave at that natural frequency then the second object will begin to vibrate at the same frequencyExample opera singer shattering glass, musical cups

Standing Waves/HarmonicsOn a string standing waves are madeb-1st harmonic natural frequencyc-2nd harmonic1st overtoneOne octave higherd-3rd harmonic2nd Overtone

WavesElectromagnetic Waves and LightTypes of WavesMechanical WavesUse a MediumTraverse (ocean waves) and Longitudinal (springs and sound)Electromagnetic WavesDo not require a mediumAre transverse wavesAre formed when an electric field is coupled with a magnetic field Light, microwaves, radiowaves etcElectromagnetic Spectrum

Rabbits Mate In Visible Unusual eXspensive GardensRadio, Microwaves, Infrared, Visible, Ultraviolet, X-rays, Gamma RaysROYGBIVRed, orange, yellow, green, blue, indigo, and violet

31Visible LightWhite light is a mixture of different colorsRed light has the longest wavelength (700 nm)Violet has the shortest (400 nm)ROYGBIV

32EM RadiationIs emitted from energized matterAfter energy is absorbed by matter it is emitted as EM radiation

Speed of LightThe speed of light=cThe speed of light is 3.0 x 108 m/s in a vacuumIF there is a medium the speed will depend on the type of mediumDenser=slower

ExampleThe sun is 1.50 x 108 km from Earth. How long does it take for the light from the Sun to reach us?d=1.50 x 108 kmd=1.50 x 1011 mc=3.0 x 108 m/s t=?v=d/t500 seconds or 8.3 min35ExampleWhat is the frequency of red light if the wavelength is 700 nm?=700 nm=7.0 x 10-9 mc=3.0 x 108 m/s f=?v=fc=f

36Waves, Sound and LightSnells LawWave SpeedWave Speed depends on the mediumWhen waves travel from one medium into another the speed will changeAs the waves moves to more shallow water the waves slow down

Wave SpeedWaves traveling perpendicular to the new medium (i=0 or angle of incidence) continue in the same directionVelocity changes, but the frequency stays constantSoo.. Wavelength will changeWhen waves are not perpendicular they will bend

RefractionRefraction-bending of a wave due to changing mediumOptical Density- a measure of how difficult it is for light to travel in a substanceVacuum