Ch. 20 Wave NotesCh. 20 Wave NotesCool Wave Effect

A. How are Waves Described ?A. How are Waves Described ?1. Introduction: 1. Introduction: (Video)

a)a) WaveWave= any disturbance that transmits energy = any disturbance that transmits energy through matter or spacethrough matter or space

b)b) Waves carry energyWaves carry energy– but the material through – but the material through which the wave travels does not move w/ the which the wave travels does not move w/ the energy- The Matter Vibrates!energy- The Matter Vibrates!

1.1. A A mediummedium - substance through which a wave can - substance through which a wave can travel (can be solid, liquid, or gas)travel (can be solid, liquid, or gas)

2.2. Mechanical waveMechanical wave = require a medium (Ex. Sound) = require a medium (Ex. Sound)

3.3. Electromagnetic waveElectromagnetic wave = can travel through a = can travel through a vacuum and do not require a medium (Ex. Visible vacuum and do not require a medium (Ex. Visible Light)Light)

2. How are waves classified based on disturbance of the 2. How are waves classified based on disturbance of the medium they travel through?medium they travel through?

((based on direction of the particles move as they vibrate compared w/ based on direction of the particles move as they vibrate compared w/ direction in which the waves travel)direction in which the waves travel)

a.a. Transverse wavesTransverse waves vibrate the particles of the medium w/ an vibrate the particles of the medium w/ an up and down motion, causing the energy to move across or up and down motion, causing the energy to move across or perpendicular to that wave. perpendicular to that wave. Video

• Crest Crest = top of the wave= top of the wave• TroughTrough = bottom of the wave = bottom of the wave• Ex: electromagnetic wavesEx: electromagnetic waves

crest

trough

b. b. Longitudinal wavesLongitudinal waves - waves that vibrate the - waves that vibrate the particles of the medium back and forth, causing the particles of the medium back and forth, causing the energy to move parallel to the wave energy to move parallel to the wave Video

• CompressionCompression - section where the particles are crowded - section where the particles are crowded togethertogether

• Rarefraction Rarefraction - section where the particles aren’t crowded - section where the particles aren’t crowded togethertogether

Ex: sound wave Ex: sound wave Video

Compression Rarefaction

c. Surface Wave c. Surface Wave = = Combination of waves that occur Combination of waves that occur at or near the boundary between two media, a at or near the boundary between two media, a transverse wave and a longitudinal wave can transverse wave and a longitudinal wave can

combinecombine Video-Surface Wave

Wave Animations Link

B. What are the Properties of Waves? B. What are the Properties of Waves? Video

1. 1. AmplitudeAmplitude is the maximum distance the wave vibrates from its rest is the maximum distance the wave vibrates from its rest position. The larger the amplitude the more energy the wave has position. The larger the amplitude the more energy the wave has and the taller the wave.and the taller the wave.

2.2.WavelengthWavelength - distance between any two adjacent crest and - distance between any two adjacent crest and compressions in a series of waves. compressions in a series of waves. Shorter Shorter λλ has higher E than has higher E than long long λλ. . Symbol= Symbol= λλ

3. 3. FrequencyFrequency= the number of waves produced in a given amount of = the number of waves produced in a given amount of time. Measured by counting the number of waves that pass in a time. Measured by counting the number of waves that pass in a certain amount of time. Expressed in Hertz (Hz); one Hertz= one certain amount of time. Expressed in Hertz (Hz); one Hertz= one wave per second. High Frequency carries more energy.wave per second. High Frequency carries more energy.

4. 4. Wave speedWave speed= the speed in which a wave travels.= the speed in which a wave travels.Formula:Formula:

wave speed (v)= wave length (wave speed (v)= wave length (λλ) x frequency (f)) x frequency (f)V= V= λλ x f x f

• The distance a single crest/ compression travels in a given The distance a single crest/ compression travels in a given timetime

• Depends on medium Depends on medium Video: Simulation

Larger Amplitude Means More Larger Amplitude Means More EnergyEnergy

What does changing amplitude do to a sound wave? What does this do to EM Wave (light)?

Which sound wave has the lowest pitch (f)? Which sound wave has the lowest pitch (f)? Highest pitch (f)?Highest pitch (f)?

Which color light has the highest Which color light has the highest frequency?frequency?

C. How do waves interact?C. How do waves interact?

1. 1. Reflection:Reflection: when a wave bounces when a wave bounces back after striking a barrierback after striking a barrier

Ex: water, sound, and light Ex: water, sound, and light waves reflectwaves reflect

Video

2. 2. Refraction:Refraction: the bending of a wave the bending of a wave as it passes at an angle from as it passes at an angle from one medium to another one medium to another because the wave is changing because the wave is changing speed as it enters another speed as it enters another medium… therefore it depends medium… therefore it depends on a mediumon a medium

VideoVideo

Reflection

Refraction

Mirror

d. d. Diffraction:Diffraction: the bending of waves around the bending of waves around a barrier or through an openinga barrier or through an opening

VideoVideo

4. 4. Interference:Interference: when two or more waves share the when two or more waves share the same space; they overlap.same space; they overlap.

a. a. ConstructiveConstructive interferenceinterference occurs when the crests of occurs when the crests of one wave overlap the crests of another wave(s). one wave overlap the crests of another wave(s). When the waves overlap, a new wave is created When the waves overlap, a new wave is created with a larger amplitude.with a larger amplitude.

b. b. Destructive Interference-Destructive Interference- occurs when the crests of occurs when the crests of one wave and the troughs of another wave overlap. one wave and the troughs of another wave overlap. The resulting wave has smaller amplitude.The resulting wave has smaller amplitude.

VideoVideo

AnimationAnimation

c. c. Standing waveStanding wave certain parts of the wave certain parts of the wave remain standing (called nodes and remain standing (called nodes and antinodes).antinodes).

The result is that the wave appears to be The result is that the wave appears to be standing still which is the result of 2 identical standing still which is the result of 2 identical

waveswaves traveling in opposite directions.traveling in opposite directions.

VideoVideo

Examples of Standing waves:

A= Antinode

N= Node

Remember:

V= f x λ

As frequency increases then the wavelength decreases.

As frequency increases the ENERGY increases

As frequency increases the amplitude increases

5.5. Resonance Resonance means resound or sound again. means resound or sound again.• All objects have a natural frequencyAll objects have a natural frequency.. • When an object is disturbed it will vibrate at its own When an object is disturbed it will vibrate at its own

special set of frequencies, producing a unique special set of frequencies, producing a unique sound. sound.

• Occurs when the vibration of an object matches Occurs when the vibration of an object matches another object’s natural frequency causing it to another object’s natural frequency causing it to vibrate. vibrate.

• The 2 objects vibrate together and an increase in The 2 objects vibrate together and an increase in the amplitude occurs.the amplitude occurs.

o Ex: Tacoma Narrows Bridge Disaster, musical Ex: Tacoma Narrows Bridge Disaster, musical instrumentsinstruments

o Tacoma Narrows Bridge VideoTacoma Narrows Bridge Videoo Wine Glass VideoWine Glass Videoo Wine Goblet ResonanceWine Goblet Resonance