Waves: Take 2

Mr. Davis

p. 3443,5,20,32,33,38,40,43,45

Review: Key characteristics of waves

Period (if axis is time)

Amplitude: The height of the wave from node to antinode (transverse waves), or the pressure in a compressive wave. Measured in units describing the wave

Frequency: The rate of occurrence of the wave (in Hertz or cycles / second)

Wavelength: The distance traversed by a full cycle of the wave Node: The “zero point” of the waveAntinode: The extreme point of the wave (max or min amplitude)Period: The time between successive waves

The frequency

f = 1/T

where T is the period.

All of these terms are required for the Regents

How does a string make music?

•What does a string look like when vibrating?

How do I measureAmplitudeWavelengthFrequencyPeriod

For each of these?

Videos: Superposition and wavelength as a function of gas composition

http://www.acs.psu.edu/drussell/Demos/superposition/superposition.html

http://www.wired.com/wiredscience/2008/09/top-10-amazing/

Standing waves

• Two similar periodic waves traveling in opposite directions form a standing wave.

L = /2

V = nf/2L

What happens when two waves collide?

What happens under the Cone of Silence?

What happens when two waves collide?

What happens when many people in the same room talk? What happens when an orchestra plays?What happens when waves interact in the ocean? (The Perfect Storm)What happens when two billiard balls collide?

They can cancel: Superposition(This is really addition of components of inverse sign)

What happens when two waves collide?

Sum

They can add: Superposition

What happens when two waves collide?

Sum

What happens when two waves collide?

They pass through each other without affecting each other and keep on going

What happens when two waves collide?

They pass through each other without changing and keep on going.(Have you ever crossed the beams of two flashlights to see what would happen?)

What happens when two waves collide?

They pass through each other without changing and keep on going.(Have you ever crossed the beams of two flashlights to see what would happen?)

http://bestphysicsvideos.blogspot.com/2011/07/mit-physics-demo-wave-superposition.html

MIT Demonstration of Bell Labs Wave machine

Series 1

-1.5

-1

-0.5

0

0.5

1

1.5

1 62 123 184 245 306 367 428 489 550 611 672 733 794

Series 1

-1.5

-1

-0.5

0

0.5

1

1.5

1 62 123 184 245 306 367 428 489 550 611 672 733 794

Series 1

Series 2

-1.5

-1

-0.5

0

0.5

1

1.5

1 48 95 142 189 236 283 330 377 424 471 518 565 612 659 706 753

Series 1

Series 2

Series 1+2

-1.5

-1

-0.5

0

0.5

1

1.5

1 47 93 139 185 231 277 323 369 415 461 507 553 599 645 691 737 783

                                   (7)

Fundamental Frequency and Harmonics

Two waves of similar frequency

Beat frequency is the difference between them

Beat Frequency

Speed of Waves

•Medium•Wavelength (frequency) •(temperature)•(pressure)

Waves have a speed!

Dependent on

•Medium•Temperature•Pressure•Frequency (wavelength)

What about light?

Speed of Waves

where v is the speed, f is the frequency, and lambda is the wavelength.

v = f

What is v for a Slinky?

What is v for sound?

What is v for light?

The relationship between wave speed, wavelength, and frequency is simple•For a given temperature, pressure, material, etc.

Speed of Waves

Medium Speed (m/sec) Frequency Wavelength

Sound 340 261

Light 300,000,000 700E-9

Ocean Wave 25 1

Tsunami 260

Earthquake P 2

Earthquake Surface

0.5

Guitar String 425 1m

http://www.pbs.org/wgbh/nova/earth/japan-killer-quake.html

Affects on sound waves

•Vibration (tension)

•Length

•Resonance

•Affects of sound waves

•Shatter glass!

•Transmit energy!

http://www.youtube.com/watch?v=w-qKlCy0T-g

Sugar Plum Fairy: http://search.yahoo.com/r/_ylt=A0oG7qUs1zlPmVoAa6YPxQt.;_ylu=X3oDMTByMTNuNTZzBHNlYwNzcgRwb3MDMgRjb2xvA2FjMgR2dGlkAw--/SIG=12095j2g1/EXP=1329219500/**http%3a//www.youtube.com/watch%3fv=QdoTdG_VNV4

http://video.search.yahoo.com/video/play?p=sugar%20plum%20fairy%20glasses&tnr=21&vid=1426162124191&l=207&turl=http%3A%2F%2Fts4.mm.bing.net%2Fvideos%2Fthumbnail.aspx%3Fq%3D1426162124191%26id%3D4ac0756f0bc1187ac6dea26ab13b8515%26bid%3DQGXvePJox3giHw%26bn%3DThumb%26url%3Dhttp%253a%252f%252fwww.youtube.com%252fwatch%253fv%253deQemvyyJ--g&rurl=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DeQemvyyJ--g&sigr=11a3bvfac&newfp=1&tit=%26quot%3BDance+of+the+Sugar+Plum+Fairy%26quot%3B+on+the+Glass+Armonica

http://www.youtube.com/watch?v=HpovwbPGEoo

Wave VideosReflection off a sea wall: http://www.youtube.com/watch?v=PevRZAxDxZwBig wave at beach: http://www.weather.com/blog/weather/8_21326.htmlhttps://www.youtube.com/watch?v=QdoTdG_VNV4&feature=player_embedded#at=131Tacoma narrows bridge: http://video.search.yahoo.com/search/video;_ylt=A2KLqIGXaSdPEn0AIxT7w8QF?p=tacoma+narrows+bridge&b=21&tnr=20