waves* a vibration or disturbance that transmits energy without transmitting mattera vibration or...

Waves*Waves*

• A vibration or disturbance that A vibration or disturbance that transmits energy without transmits energy without transmitting mattertransmitting matter

http://www.e-prolab.com/comlab/overview/video/wav-t-trans.gif

Mechanical Waves*Mechanical Waves*

• Waves that need a medium or Waves that need a medium or material to transmit energy (water material to transmit energy (water waves, sound waves, etc.)waves, sound waves, etc.)

Waves

Electromagnetic Waves*Electromagnetic Waves*

• Waves that can transmit energy without Waves that can transmit energy without a medium or material to travel through a medium or material to travel through (light waves, heat waves, any waves in (light waves, heat waves, any waves in space, etc.)space, etc.)

http://www.thebrain.mcgill.ca/flash/capsules/images/outil_bleu16_img01.jpg

Cutnell & Johnson, Wiley Publishing, Physics 5th Ed.

LONGITUDINAL WAVES*LONGITUDINAL WAVES*

• Waves in which the medium Waves in which the medium vibrates parallel to the direction of vibrates parallel to the direction of wave travelwave travel

http://www.gcse.com/waves/images/longitudinal.gif

LONGITUDINAL WAVES*LONGITUDINAL WAVES*

RarefactionRarefaction• areas where the medium is spread outareas where the medium is spread outCompressionCompression• areas where the medium is pushed areas where the medium is pushed

togethertogether

http://www.gcsescience.com/pwav7.htm

LONGITUDINAL WAVESLONGITUDINAL WAVES • The wavelength can be measured as The wavelength can be measured as

the distance between the center of the distance between the center of two compressions two compressions

• Examples of longitudinal wavesExamples of longitudinal waves1. Sound.1. Sound.2. P waves from earthquakes2. P waves from earthquakes

Longitudinal Waves

TRANSVERSE WAVES* TRANSVERSE WAVES*

• Waves in which the Waves in which the medium vibrates medium vibrates perpendicular to the perpendicular to the direction of wave traveldirection of wave travel


www.physics.ohio-state.edu/ ~phys133/demo/

TRANSVERSE WAVES TRANSVERSE WAVES • Most other types of waves are Most other types of waves are

transverse (electromagnetic waves, transverse (electromagnetic waves, s waves from earthquakes, etc.)s waves from earthquakes, etc.)

Transverse Waves

AMPLITUDE (A)* AMPLITUDE (A)* • measured from the peak (or trough) to the measured from the peak (or trough) to the

mid-pointmid-point• the maximum displacement from the the maximum displacement from the

average positionaverage position• proportional to proportional to

how much how much

energyenergy

the wave hasthe wave has


WAVELENGTH (WAVELENGTH (λλ)*)*• the distance between two peaks or the the distance between two peaks or the

distance between two troughsdistance between two troughs

• the distance the wave has traveled during the distance the wave has traveled during one complete cycleone complete cycle

• measured in metersmeasured in meters


Copywrited by Holt, Rinehart, & Winston

FREQUENCY (f)*FREQUENCY (f)*

• the number of complete cycles in one the number of complete cycles in one secondsecond

• Hertz is the unit of frequency (symbol Hz).Hertz is the unit of frequency (symbol Hz).

s

cyclesHz


PERIOD (T)* PERIOD (T)*

• the time taken for one complete cyclethe time taken for one complete cycle• unit is secondsunit is seconds


Wave Speed Equation*Wave Speed Equation*

• Speed is the frequency multiplied by the Speed is the frequency multiplied by the wavelength, unit of meter/second wavelength, unit of meter/second

fv

v

f f

v

Wave ProblemWave Problem

• A sound wave has a frequency of 3250 A sound wave has a frequency of 3250 Hz and a wavelength of 0.1 m. What is its Hz and a wavelength of 0.1 m. What is its velocity?velocity?

Source: http://www.gcsescience.com/pwav7.htm

What type of wave is an ocean What type of wave is an ocean wave?wave?

A.A. TransverseTransverse

B.B. LongitudinalLongitudinal

C.C. Combination of BothCombination of Both

Ocean WavesOcean Waves

• are neither transverse are neither transverse nor longitudinal but a nor longitudinal but a combinationcombination

• Water molecules move in Water molecules move in nearly circular pathsnearly circular paths• includes both a transverse includes both a transverse

and longitudinal and longitudinal componentcomponent


http://www.onr.navy.mil/focus/ocean/motion/waves1.htm

http://www.blueyonder.com/features/landlubbers-guide.html

http://www.onr.navy.mil/focus/ocean/motion/waves1.htm

RayRay

• An arrow drawn on a diagram to An arrow drawn on a diagram to show the direction of propagation show the direction of propagation (movement) of a set of waves(movement) of a set of waves

• A ray is always at A ray is always at 90°90° to the to the wavefrontwavefront

Why do you hear an echo if you Why do you hear an echo if you yell in a canyon?yell in a canyon?

• What is the What is the phenomena behind phenomena behind both of these?both of these?

Why do you see an image of Why do you see an image of yourself when you look in a yourself when you look in a mirror?mirror?

Reflection of Waves*Reflection of Waves*

Law of Reflection Law of Reflection • When a wave reaches When a wave reaches

the boundary between the boundary between two media, some or all two media, some or all of the wave bounces of the wave bounces back into the first back into the first mediummedium

• The angle of incidence The angle of incidence is equal to the angle of is equal to the angle of reflectionreflection..

http

://li

brar

y.th

inkq

uest

.org

/261

62/f

ig3-

1.gi

f

Reflection of WavesReflection of Waves

• All waves can be All waves can be reflected.reflected.

• A wave is reflected at A wave is reflected at thethe boundary of the boundary of the medium medium through which through which it is traveling or at any it is traveling or at any point where there is a point where there is a change in the change in the wave wave velocityvelocity..


Reflection

Wave TerminologyWave Terminology

Copywrited by Holt, Rinehart, & WinstonCopywrited by Holt, Rinehart, & Winston

How could you tell if the end of a How could you tell if the end of a rope is fixed or not if you could rope is fixed or not if you could not see the other end?not see the other end?

If the rope is attached, a If the rope is attached, a wave would?wave would?

A. reflect back on the A. reflect back on the same side as it was same side as it was transmitted (in phase).transmitted (in phase).

B. Reflect back on the B. Reflect back on the opposite side as it was opposite side as it was transmitted (out of transmitted (out of phase)phase)

C. Would not reflect C. Would not reflect backback

Copywrited by Holt, Rinehart, & Winston

Reflections of waves*Reflections of waves*

• at a Fixed Endat a Fixed End

• A phase change A phase change occursoccurs

• at a Free Endat a Free End

• No phase change No phase change occursoccurs



Reflection at a Point where the Reflection at a Point where the Wave Velocity ChangesWave Velocity Changes

When there is a change of mediumWhen there is a change of medium

• the speed of the wave changes the speed of the wave changes • some of the energy of the incident some of the energy of the incident

wave is wave is reflectedreflected and some is and some is transmittedtransmitted

A stiff spring is attached to the end A stiff spring is attached to the end of a slinky, if a wave is sent through of a slinky, if a wave is sent through the stiff spring what will happen at the stiff spring what will happen at the junction with the slinky?the junction with the slinky?

A.A. All of the wave will be reflected backAll of the wave will be reflected back

B.B. None of the wave will be reflected backNone of the wave will be reflected back

C.C. Some of the wave will be reflected back and Some of the wave will be reflected back and the reflected part will be in phase.the reflected part will be in phase.

D.D. Some of the wave will be reflected back and Some of the wave will be reflected back and the reflected part will be out of phase.the reflected part will be out of phase.

How is this like the fixed/loose end result?How is this like the fixed/loose end result?

Reflection at a Point where the Reflection at a Point where the Wave Velocity Changes*Wave Velocity Changes*

When vWhen v22 > v > v11

• Transmitted wave, no phase change.Transmitted wave, no phase change.• Reflected wave, phase change.Reflected wave, phase change.

http://www.saburchill.com/physics/chap04.html

http://www.saburchill.com/physics/chap04.htmlhttp://www.physicsclassroom.com/Class/sound/u11l5b.htmlhttp://www.physicsclassroom.com/Class/sound/u11l5b.html

Reflection at a Point where the Reflection at a Point where the Wave Velocity Changes*Wave Velocity Changes*

When vWhen v22 < v < v11

• Transmitted wave, no phase change.Transmitted wave, no phase change.• Reflected wave, no phase change.Reflected wave, no phase change.



Refraction*Refraction*

• When waves travel across a When waves travel across a boundary between two different boundary between two different media, their speed changes. media, their speed changes.

• The change in speed The change in speed

results in a change in results in a change in

directiondirection

of the waves.of the waves.

Refraction

RefractionRefraction

http://science.uniserve.edu.au/school/curric/stage6/phys/communicates/Student_section/student_physics/physics_pics/animated_refraction2.gif

http://www.studentxpress.ie/educ/physics/physics3/refrac1.gif

Hall Wanderer QuestionHall Wanderer Question

If you are standing in the hall beside a If you are standing in the hall beside a classroom door, can you hear the classroom door, can you hear the teacher inside the class?teacher inside the class?

a.a. YesYes

b.b. NoNo

How is this possible?How is this possible?


DiffractionDiffraction

Diffraction occurs when waves spread out after Diffraction occurs when waves spread out after passing through a gap or round an obstacle.passing through a gap or round an obstacle.

Sea wave diffraction

Diffraction becomes Diffraction becomes more significant more significant when the size of the when the size of the gap or obstacle is gap or obstacle is reduced compared reduced compared with the wavelength with the wavelength of the wave.of the wave.

Boundaries and WavesBoundaries and Waves

Incident Wave: wave that strikesthe boundary

Reflected Wave: wave that returnsin the larger spring

For a wall boundary, if little energyis transmitted into the wall the wave may have the same amplitude, butbe inverted

Superposition of WavesSuperposition of Waves

• The The principle of superposition principle of superposition states states that the displacement of a medium that the displacement of a medium caused by two or more waves is the caused by two or more waves is the algebraic sum of the displacements algebraic sum of the displacements caused by the individual waves.caused by the individual waves.

• Two are more waves can combine to Two are more waves can combine to form a new wave.form a new wave.

Wave InterferenceWave Interference• The result of the superposition of two or The result of the superposition of two or

more waves is called more waves is called interference.interference.

• ConstructiveConstructive interference occurs when the interference occurs when the waves are in sync (in phase), and they combinewaves are in sync (in phase), and they combine

• Destructive Destructive interference occurs when the interference occurs when the waves are out of sync, and the cancel some or waves are out of sync, and the cancel some or all of each other out.all of each other out.

Constructive InterferenceConstructive Interference

Destructive InterferenceDestructive Interference

Interference PatternsInterference Patterns

• Interference can be Interference can be observed in all types of observed in all types of waves. waves.

• The diagrams represent The diagrams represent the interference pattern the interference pattern due to two sets of water due to two sets of water waves of identical waves of identical frequency, produced byfrequency, produced by point sources point sources which are which are oscillating in phase with oscillating in phase with each other.each other.

Waves from source 1

Waves from source 2

Interference Pattern Interference Pattern

of higher frequency oscillations

http://www.calvin.edu/~lmolnar/anim/circ1.gif

Interference PatternsInterference Patterns2 identical waves 2 identical waves Double amplitude of the wave Double amplitude of the wave


Interference PatternsInterference PatternsOffset waves Offset waves Areas of constructive and destructive interference Areas of constructive and destructive interference


Interference PatternsInterference PatternsWider spacing of sources- more lines of interferenceWider spacing of sources- more lines of interference


Standing Waves*Standing Waves*

• Reflection of waves at certain Reflection of waves at certain frequencies produce areas of frequencies produce areas of constructive and destructive interferenceconstructive and destructive interference

• Appears to be stationaryAppears to be stationary• Nodes = areas where medium has no Nodes = areas where medium has no

amplitudeamplitude• Anti-nodes = areas of maximum Anti-nodes = areas of maximum

amplitudeamplitude

Standing WavesStanding Waves

http://www.hamline.edu/~arundqui/phys1140/animations/standingwave.gif

http://www.calvin.edu/~lmolnar/anim/sw.gif

waves* a vibration or disturbance that transmits energy without transmitting mattera vibration or...

Documents

sound waves

s waves

types of waves

heat waves

light waves

mechanical waves

p waves

transverse waves slide