Wave Basics – Day 1Wave Basics – Day 1

Fill in the blank:Fill in the blank:

Waves transmit Waves transmit ________.________.energyenergy

What is a wave?What is a wave?

Disturbance that carries Disturbance that carries energy through a medium (air, energy through a medium (air, water, etc.) or spacewater, etc.) or space

Energy “spreads out” as a wave travels

Energy “spreads out” as a wave travels

wave front

2 Categories2 Categories

1. Mechanical – requires a 1. Mechanical – requires a mediummedium

2 Categories2 Categories

2. Electromagnetic – does not 2. Electromagnetic – does not need a mediumneed a medium

Mechanical WavesMechanical Waves

2 Ways to Classify

TransverseLongitudinal

Parts of a Transverse WaveParts of a Transverse Wave

Transverse Waves

Medium vibrates perpendicular to direction of wave travel

Longitudinal Waves

Medium vibrates parallel to direction of wave travel

Parts of a Longitudinal WaveParts of a Longitudinal Wave

Lab – Wave Behavior

Waves – Day 2

Wave PropertiesWave Properties

Wavelength ( )

Distance between 2 identical parts of a wave

Unit – m

Period (T)

Time for one full wavelength

Unit - s

Frequency ( f )

# of waves that pass by a given point per second

Unit - Hz

Sound Frequency RangesSound Frequency Ranges

Frequency Generator DemoFrequency Generator Demo

Light FrequenciesLight Frequencies

Electromagnetic SpectrumElectromagnetic Spectrum

Frequency and Period

Higher frequency = less time

f = 1/T

Wave SpeedWave Speed

Depends on the mediumDepends on the mediumApprox. 340 m/s in airApprox. 340 m/s in air3-4 Xs faster in water3-4 Xs faster in water15 – 20 Xs faster in solids15 – 20 Xs faster in solids

Why differences?Why differences?

Density of medium determines Density of medium determines speedspeed

Speed of Light (c)Speed of Light (c)

Light is EMG wave – requires Light is EMG wave – requires no mediumno medium

3 X 103 X 1088 m/s in space m/s in spaceSlower in air and waterSlower in air and water

Wave MathWave Math

EquationsEquations

Lab – Modeling Transverse Lab – Modeling Transverse WavesWaves

Wave Interaction, etc. – Cover Wave Interaction, etc. – Cover on Day 3on Day 3

ReflectionReflection

Not only light raysNot only light raysBouncing back of wave when Bouncing back of wave when

it meets surface or boundaryit meets surface or boundary

DiffractionDiffraction

Bending of a wave as it Bending of a wave as it passes an edge or an openingpasses an edge or an opening

RefractionRefraction

Bending of waves as they Bending of waves as they pass from one medium to pass from one medium to anotheranother

InterferenceInterference

Combination of waves that Combination of waves that exist in the same place at the exist in the same place at the same timesame time

ConstructiveConstructiveDestructiveDestructive

Constructive InterferenceConstructive Interference

Destructive InterferenceDestructive Interference

Standing WavesStanding Waves

Caused by constructive Caused by constructive interferenceinterference

Nodes – 0 amp.Nodes – 0 amp.Antinodes – max amp.Antinodes – max amp.

Standing WavesStanding Waves

Forced VibrationForced Vibration

One object One object forces forces another to another to vibratevibrate

Natural FrequencyNatural Frequency

An objects inherent frequencyAn objects inherent frequencyFrequency at which an object, Frequency at which an object,

once energized, will vibrateonce energized, will vibrate

ResonanceResonance

Increase in amplitude when Increase in amplitude when the forced vibration equals the forced vibration equals the natural frequency of the the natural frequency of the vibrationvibration

Tacoma Narrows Bridge, 1940Tacoma Narrows Bridge, 1940

Sound and Light – Cover on Day 4Sound and Light – Cover on Day 4

What are sound waves?What are sound waves?

Longitudinal Longitudinal waves waves

Pressure Pressure variations variations transmitted transmitted through matterthrough matter

PitchPitch

Pitch = frequencyPitch = frequencyHuman hearing – 20 Hz Human hearing – 20 Hz

to 20,000 Hzto 20,000 Hz

Sound Waves and PitchSound Waves and Pitch

Wave fronts compressed as Wave fronts compressed as object moves toward you – object moves toward you – higher pitchhigher pitch

Wave fronts spread apart Wave fronts spread apart when moving away – lower when moving away – lower pitchpitch

Doppler graphic Doppler graphic

Doppler EffectDoppler Effect

Observed change in the Observed change in the frequency of a wave when the frequency of a wave when the source (or observer) is movingsource (or observer) is moving

Electromagnetic WavesElectromagnetic Waves

Electric and magnetic Electric and magnetic fields of moving chargesfields of moving charges

No medium neededNo medium neededv = c = 3.00 X 10v = c = 3.00 X 1088 m/s m/s

ElectromagnElectromagnetic Wave etic Wave PicturePicture

Electromagnetic SpectrumElectromagnetic Spectrum

How do Polaroid How do Polaroid glasses work?glasses work?

Polarization of Light Polarization of Light PicturePicture

picturepicture

PicturePicture

PolarizationPolarization

Polarizing material Polarizing material contains slots allowing contains slots allowing only 1 direction of light only 1 direction of light waves to pass throughwaves to pass through

Color and LightColor and Light

An apple looks red because…An apple looks red because…All light except red is absorbed; All light except red is absorbed;

red light is reflectedred light is reflected

Color and Light video?Color and Light video?