Electromagnetic Induction and Wave Characteristics

Bellringer



What is electromagnetic induction and who explained

it?



Why does your debit card have a black strip on the

back?



SLC today



E&M Quiz



10 questions



3 MC, 6 written, 1 drawing



Scientists



Electromagnetic Induction, Electromotive force



Magnetic field lines



Electric motors/generators



Transformers, solenoids, railgun, speakers, etc.

Surf’s up dude!

Objectives



Learn the basic characteristics of waves and use them

to solve simple problems.



A wave is a disturbance that carries energy through

matter or space without transferring matter.



Wave Demo



Amplitude

: The greatest

distance from

equilibrium.



The bigger the amplitude

of the wave, the more

energy the wave has.



Crest:

 The top point of a wave.



Trough:

 The bottom point of a wave.



Wavelength:

 The shortest distance between points

where the wave pattern repeats itself.



Phase:

 Any two points on a wave that are one or more

whole wavelengths apart are said to be “in phase”.



Frequency: 

Is the number of complete oscillations a

point on that wave makes each second.

Practice



On page 393 of the textbook answer questions 15, 16,

17, 19, 22, and 24.

Answers



15. 343m/s, 2.29x10^-3s, 0.787m



16. You should shake it at a lower frequency because

wavelength varies inversely with frequency.



17. 2.45m/s



19. 2.50m



22. The frequency is one-half of its original value.



24. The wavelength increases to 1.5 times its original value.



What does a wave

transfer?



Energy, NOT MASS!

 STOP

Objectives



Review and solidify the material you learned and

practiced yesterday.



Learn about the different types of waves.



Study, create, and destroy different wave types.

Practice



On page 393 of the textbook answer questions 15, 16,

17, 19, 22, and 24.

Answers



15. 343m/s, 2.29x10^-3s, 0.787m



16. You should shake it at a lower frequency because

wavelength varies inversely with frequency.



17. 2.45m/s



19. 2.50m



22. The frequency is one-half of its original value.



24. The wavelength increases to 1.5 times its original value.

Art Time – Example Part Two



Draw two more cycles of the red wave.

Art Time – Example Part Two



Draw one more cycles of the blue wave.



What is the wavelength of the red wave?



2.0m



What is the wavelength of the blue wave?



4.0m



What is the amplitude of the red wave?



0.5m



What is the amplitude of the blue wave?



0.25m



If this is a snapshot of how far each wave traveled in 1

second, what is the frequency of the red wave?



3.0Hz



If this is a snapshot of how far each wave traveled in 1

second, what is the frequency of the blue wave?



1.5Hz



Are the red and blue wave in phase with each other?



Nope

You try



Draw the following waves on the same graph:

1.

A wave with an amplitude of 6m and a wavelength of

3m.

2.

A wave with an amplitude of 2m and a wavelength of 2m.

3.

A wave with an amplitude of 3m and a wavelength of

4m.



Which wave has the greatest frequency if they’re all

traveling at the same speed?



There are two types of waves!

1.

Transverse Waves

: A wave that disturbs the particles

in the medium perpendicular to the direction of the

wave’s travel.

2.

Longitudinal Waves

: A wave that disturbs the

particles in the medium parallel to the direction of

the wave’s travel.

Checkpoint

1.

What is a Transverse wave?

2.

What is a Longitudinal wave?



How can a single transverse wave pulse be produced

using a slinky?



How can a single longitudinal wave pulse be produced

using a slinky?



Sound waves are longitudinal waves because they shake

the air as they transfer the energy to our ears.



https://www.youtube.com/watch?v=XFF2ECZ8m1A

Must Watch Television

 STOP

Objectives



Learn about the different types of waves.



Study, create, and destroy different wave types.

Grade Update



Answer these questions.

1.

How did you follow your plan on how to improve

your grade?

2.

Are you happy with your grade and what do you want

your grade to be by the end of the quarter?

3.

What are you going to do to improve your grade?

Waves at Boundaries



What does the surface of water look like when you

drop a small rock in a calm bucket of water?



What happens when the wave hits the walls?



Splash Demo!!! Get your goggles!



Recall that a wave’s speed depends on the medium it

passes through:



Water depth



Air temperature



Tension, and mass



A “

Boundary

” is when a wave goes from one medium

to another.



There are three ways you’ll be interested in at

boundaries.

1.

Incident Wave

: A wave pulse that strikes the

boundary.

2.

Reflected Wave

: A wave that bounces backwards

after hitting the boundary.

3.

Transmitted Wave

: A wave that continue forward

after hitting the boundary.



Different Medium Demo:



The incident energy is split between reflected and

transmitted energy.



Rigid Boundaries Demo:



All of the incident energy is turned into reflected

energy.

Checkpoint

1.

How does the amplitude (energy) of a wave change

when it hits a rigid boundary like a wall?

2.

How is the conservation of energy observable with a

single wave hitting a different medium?

Waves in a Bucket



What happens if you drop two rocks into a calm

bucket of water instead of just one?



Splash Demo 2.0!!! Get dem goggles back!



The waves seem to hit each other, but then just

continue on their way…weird?



When we had two particles (carts) and pushed them

into each other they collided and then stopped.



When waves collide they temporarily interfere with

one another, but they do not stop each other.



The 

Principle of Superposition

 states that the

displacement of a medium caused by two or more

waves is the algebraic sum of the displacements caused

by the individual waves.

Now a super superposition demo!

1.

Can we make two waves create a bigger wave?

2.

Can we make two wave create a smaller wave?

3.

Is there a limit to how many waves we can create?

 STOP

Objectives



Learn about the different types of interference,

practice solving problems that deal with it, and

demonstrate the different interference patterns with a

small group.

Limit to waves?



The number of waves that are interfering with each

other is limitless.



Each wave is just a form of a sine wave.



Wolfram Alpha Demo:



https://www.wolframalpha.com/input/?i=sinx

+



There are three types of interference

1.

Constructive Interference

: When the crest of a wave

meets a crest of another wave of the same frequency at

the same point.

2.

Destructive Interference

: When the crest of a wave

meets a trough of another wave of the same frequency at

the same point.

3.

Different Amplitude

: All other scenarios of waves

interference.

Constructive vs. Destructive



Which is constructive and which is destructive

interference?  How do you know?

Can you do this?



Let’s see if we can successfully make waves both

constructively and destructively interfere!



Note: not all the slinkies are in the best shape, but

remember this is not an open invitation to make them

worse!

Can you do this?



Try to complete these 5 missions.  Try to take video or

pictures with your phone to capture the interference.

1.

Make two transverse waves constructively interfere.

2.

Make two longitudinal waves constructively interfere.

3.

Make two transverse waves destructively interfere.

4.

Make two longitudinal wave destructively interfere.

5.

Play around with different amplitudes, can you get three

waves to interfere?



Draw a picture of two

waves moving towards

each other that will

constructively interfere

once their crests meet.

 STOP

Objective



Learn and be able to identify standing waves and their

properties.

Results? – Where are they?



What were you able to find?



E-mail me your successful results!



KVerspoor@windsor-csd.org



Were there any trials that didn’t work?

Grade Update - Labs



Answer these questions.

1.

How did you follow your plan on how to improve

your grade?

2.

Are you happy with your grade and what do you want

your grade to be by the end of the quarter?

3.

What are you going to do to improve your grade?

Homework



Read pages 394 to 397.



Stop before reading “Waves in Two Dimensions” on

page 397



Very good illustrations and snapshots of superposition

and interference.



When a wave appears to just move up and down

instead of transmitting energy side to side it is called a

standing wave.



These waves appear to be standing still, hence

“Standing Wave”.



What happens to the number of bumps as I increase

the frequency?  Why?



How does the wavelength change has I increase the

frequency?



How does the speed of the waves change as I increase

the frequency?



Why must I keep oscillate my arm to generate a

standing wave?



A standing wave is made up interfering waves moving

in opposite directions.  Without this small input the

wave would die out.



Resonance is when a small energy input frequency is

continually applied to an object and it causes the object to

oscillate with greater and greater amplitude.



Resonance is continual constructive interference.



Every object has a resonance frequency.



Swing-sets use resonance.



Microwave ovens are the resonance frequency of water.



Tesla found the resonance frequency of the Earth.



https://www.youtube.com/watch?v=xox9BVSu7Ok



The designer took Tacoma’s money and said he

brought and insurance policy for the bridge…he didn’t



The bridge started oscillating almost as soon as it was

finished.



It collapsed just days before the fake insurance policy

would have expired.



He went to jail.



Nodes and Antinodes are used to help describe and

understand waves.



A “node” is where waves meet and cause zero

displacement of the medium.



No displacement



An “antinode” is where waves meet and cause the

largest displacement of the medium.



Anti no displacement

Nodes and Antinodes

Nodes and Antinodes

Practice



How many nodes and antinodes does the wave below

have?

FYI



The mod 8 physics class is smoking the mod 2 physics

class…90 to 84!

Practice



Page 403 numbers 61-63, 67, 71-74, 76



17 minutes to complete.



Work in pairs or groups of three.



Each group can ask me up to three questions.



Counts as a grade…homework? Quiz? Lab? Test?

61.

T=8.3s

62.

4.0 m/s

63.

v=0.288 m/s ; T=0.21s

67.

f=550Hz ; 275 waves ; 165m

71.

The reflected wave pulse from a rigid boundary is

inverted.

72.

No displacement or movement

73.

Bare areas are antinodes, sugar covered areas are

nodes

74.

A standing wave exists and the string can be touched

at any of its five nodes

76.

See drawing.



What is a standing wave?



What is an antinode?



What is a node?

 STOP

Objectives



Practice your understanding of waves.



Complete “Slinky Lab” to demonstrate you have the

power to create and destroy waves.



Computer simulator.

Slinky Lab



All sample calculations must be shown on a separate

sheet of paper.



All answers to questions must be shown on a separate

sheet of paper.



All questions must be answered in complete sentences

with full explanation.



1 tile is 1 meter.



Turn it in on the back

table and pick up your

bellringer from last week

as well as your group’s

answers from last week.



How are standing waves

created?

 STOP



What is a standing wave?



How are standing waves created?



What is an antinode?



What is a node?

Objectives



Review the basics of waves for a quiz tomorrow.

Labs



Please pass up your slinky labs



15 multiple questions?



3 long answers?



1 mod



Tuesday?



In the “Intro to Waves HW” packet answer questions

35 (parts 1-3), 35, 36, 37



Yes there are two number 35s



For homework finish the packet!

Standing Wave Simulator



What does a standing longitudinal wave look like?



https://phet.colorado.edu/en/simulation/normal-

modes



Fixed end vs. open end.  Destructive and Constructive

Interference



https://phet.colorado.edu/en/simulation/wave-on-a-

string



Wave Vocabulary



Drawing Waves



Transverse vs. Longitudinal Waves



Wave interference and Superposition



Constructive/Destructive



Standing Waves



Nodes and Antinodes



Turn it in on the back table

and pick up your bellringer

from last week as well as

your group’s answers from

last week.



If a wave travels at 15m/s

and has a wavelength of

2.2m what is its frequency?

 STOP

Objectives



Review the basics of waves for a quiz tomorrow.

Intro to Waves HW



You know all the topics that will be on the quizest.

Can you use this knowledge to figure out the questions

I’ll ask?



Write 2 multiple choice questions and 1 long answer

question with at least 2 parts.



Try to cover as many of those categories as possible.

You be the teacher!



I’ll collect and redistribute the questions.



Find your partner then solve the questions you are

given.



Then you’ll grade their responses.



Who had good questions?

Intro to Waves HW Packet

Physics teacher wave generator



https://www.youtube.com/watch?v=-gr7KmTOrx0