Waves and Energy Transfer

14.1 Wave Properties

Wave

• A repeating disturbance or movement that transfers energy through matter or space

Mechanical Waves

• Require a medium

• Can be Transverse and Longitudinal

Electromagnetic Waves

Do NOT need a medium to travel throughElectromagnetic waves are Transverse waves

Electromagnetic Wave

• A disturbance (wave) in electrical and magnetic fields

• Does not require a medium

Types of

Matter Wave

• Wave-particle duality of matter

• Quantum Mechanics

Transverse Waves• Disturbance is perpendicular to the direction of

travel

Longitudinal Waves• Disturbance is parallel to the direction of travel

• AKA Compressional waves

• All longitudinal waves are mechanical waves

Water Surface Waves• Both transverse and

longitudinal

Wave Pulse• A single disturbance that travels through a medium

The Measures of a Wave

Crest & Trough

Wavelength

• The distance from crest to crest

• One Cycle

• Lambda

The Period

• The amount of time it takes for one complete cycle

Frequency

• 1 Hz is 1 wave per second

The number of waves per secondMeasured in Hertz (Hz)

Wave Velocity

Amplitude• The Height of the wave

• Equals the wave energy

Behavior of Waves

• Diffraction

• Refraction

• Reflection

• Interference• Constructive• Destructive

Interference • Two or more waves traveling through a medium at the same time

• Constructive – increases amplitude

• Destructive – decreases amplitude

Standing Waves

• Node• Antinode

Reflection• Normal line – right angle to barrier• Angle of Incidence• Angle of Reflection

The Law of Reflection

Refraction

• The change in the direction of a wave at the boundary of two different media

Diffraction

The bending of a wave around an obstacle or an edge

SoundProperties of Sound

Sound Waves• Sound waves are longitudinal (compressional) waves

in matter

If a tree falls in a forest and no one hears it, does it make a sound?

Loudness and Pitch

Amplitude

Frequency

Velocity of Sound Waves

• Depends on the medium and the temperature

Reflection of Sound Waves

• Echo

Doppler Effect• The apparent change in the frequency (pitch) of

waves because of the relative motion between an observer and the wave source

Doppler Effect Equation:Calculate observed frequency of an object moving toward a stationary observer

While standing near a railroad crossing, a person hears a distant train horn. According to the train's engineer, the frequency emitted by the horn is 440 Hz. The train is traveling at 20.0 m/s and the speed of sound is 346 m/s.What is the observed frequency that reaches the bystander as the train approaches the crossing?

467 Hz

Red Shift and Blue shift

Sonic Boom• A shock wave caused by merging sound waves

Sound Level

• Decibels• 10-dB is

twice as loud

LightLight Fundamentals

Electromagnetic Radiation• Visible light wavelength 400-700 nm

Wave lengths of visible light• Different

wavelengths of light equal different colors

• ROYGBIV

The speed of Light• And all other

EM waves

Photon• A particle of light

Sources of LightLuminous Body

• Emits light wavesIlluminated Body• Reflects light

Incandescent Object• Emits light because it is extremely hot

Luminous Flux (P)• The rate at which light is emitted• A 100-watt bulb emits 1750 lumen

Illuminance (E)• The Illumination of a surface• Lumens per square meter (lux or lx)

Illuminance equation• P is the lumens

Inverse Square Law• If the distance doubles, the intensity decreases by a

factor of 4

Candela (cd)• A measure of luminous intensity

• Increase flux, decrease distance

• The SI unit for light intensity

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