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# Waves

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by

## Justin Alfeche

on 21 February 2014

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#### Transcript of Waves

Waves
Wave Propagation
A wave is a rhythmic disturbance that carries energy through matter or space.
Wave Characteristics
Waves travel through the earth from inside to outside. Since the different layers of the earth have different physical properties and temperatures, the speed of the waves through them will differ.
Speed of a Wave
The speed of a wave is equal to the product of its wavelength and frequency. A wave's amplitude does not affect its speed or frequency.
Warm Up 2/6
1. What is the speed of a water wave having a wavelength of 2 m and a frequency of 0.2 Hz?

(No Warm Up)
Warm Up 2/4
Write down three examples of waves you encounter in nature or everyday life.
Transverse wave
wave that vibrates perpendicular to the direction of wave motion
highest point is the
crest
lowest point is the
trough
Longitudinal Wave
disturbance travels in the same direction as, or parallel to, the direction of wave motion
Surface waves
waves at the surface of a body of water move in a direction that is both parallel and perpendicular to the direction of wave motion
surface waves have properties of both transverse and longitudinal waves
Amplitude
The amplitude of a wave is related to the energy the wave takes.
Bigger amplitude=higher energy
Waves transfer energy, but they do not transfer matter
λ (Greek, "lambda"): symbol for wavelength
f: symbol for frequency
Wave Motion
Waves that transfer energy through a vacuum and do not need a medium (a material to pass through) are electromagnetic waves.
Waves that transfer energy through a medium are called mechanical waves.
Mechanical Waves
Waves such as sound waves, ocean waves, and seismic (earthquake).

Electromagnetic Waves
EM waves are produced by the movement of charged particles resulting in changes in electric and magnetic fields.
EM waves consist of two waves that are oscillations of the electric and magnetic fields. They travel in the direction that is at right angles to the oscillation direction of both fields.
EM Waves
Speed: EM waves travel at 300,000,000 m/s through a vacuum
Sound waves travel at 343 m/s through air at 20C. How does this explain the phenomena of thunder and lightning?
No Medium Required: Radiation in EM waves can pass through solids, liquids, or gases.
Electromagnetic Spectrum: range of all possible wave frequencies of EM radiation that includes the visible light spectrum.
high frequencies: UV, x-ray, gamma
Amplitude is max distance particles in a wave's medium vibrate from their rest point.
Wavelength is the distance from crest to crest or trough to trough; units are meters
Frequency (f): number of waves that pass a certain point each second; units are Hertz (Hz)
Period (T): Time for one wavelength to pass a certain point; units are seconds (s); T=1/f
contain regions of high and low density known as
condensations
and
rarefactions
longitudinal waves are also known as compression waves
Fluids only transmit longitudinal waves (i.e. sound)
examples: ocean waves, seismic P (primary) waves, sound waves
Warm Up 2/5
A(n) _______ wave requires a medium in order for it to propagate.

A(n) _________ wave does not require a medium and can travel through a vacuum.

(Write out full statements)
2. A wave traveling at 3.0 m/s has a frequency of 0.5 Hz.
What is the wavelength of the wave?

New grades are posted (just missing test extra credit). If you are missing anything, turn it in by TOMORROW.
Also, I will be checking notebooks starting next Friday. Rubric for grading will be posted soon.
Need the notes? They're here: https://edmo.do/j/vdeazz (code: 44w9rh)
Warm Up 2/7
5 waves occur in the time span of .25 seconds.
What are the frequency and period?
(frequency= # waves per second)
When you finish your warm up, continue working on your Wave Characteristics worksheet.
Have those turned in by the end of class today.
Need the notes? They're here: https://edmo.do/j/vdeazz (code: 44w9rh)
Warm Up 2/10
Draw a picture of a transverse wave.
Label the crest, trough, amplitude, and wavelength.
Which of the following has the highest frequency?
Today we will conduct a lab over transverse and longitudinal waves.

Please organize into groups of three (or four if needed) and find a lab table to work at. Each group must have at least one member with a stopwatch on their phone. There will be two groups to each table.

When your group has formed and has found a spot at a table, send one representative to me to collect your materials.
Please start wrapping up your measurements and return your slinky, meter stick, and group student journal (with member names on it) to me.

We will continue the lab tomorrow if more time is needed.
Lab Rules
1. Use materials and behave appropriately
Any inappropriate use of materials or actions will lead to a loss of points on the lab.

Damaged slinkies will be replaced by YOU. (either buy a new one or pay \$3)
2. All members must participate/contribute.
Any members off task will lose points on their lab.
Playing Flappy Bird will result in double points off.
3. Return materials to Mr. Alfeche when class is over.
4. No eating or drinking at the lab table
Any food must be left at the desks. Points off if not.

Reminder: Notebook check starts Friday. We will have a test over waves next Tuesday (Monday off)!.
Question of inquiry:
How does the behavior of a transverse wave differ from that of a longitudinal wave?
Warm Up 2/11
In a longitudinal wave, the areas of high density are known as ___________.
The areas of low density are known as __________.
Notebook Check Rubric

30 pts: Thermodynamics Notes
10 pts: Laws of TD Foldable
30 pts: Waves Notes
30 pts: Warm Ups 1/23, 27-30, 2/4-7, 10-14

Need to study vocab for the upcoming test?
http://quizlet.com/36031861/waves-flash-cards/
**Updated grades are posted. All missing work must be turned in by the end of class next Tuesday or it will be a
zero.
Remember to use the materials appropriately.
2/12- No Warm Up
We will continue/finish the lab. Split up into your lab groups, and I will give your materials to you.
Turn in your Wave Characteristics Worksheet and any other missing work if you have not done so already.
Remember, notebook checks start Friday!
Warm Up 2/13
1.The material through which a wave travels is known as the _________ .
2. A space devoid of matter is known as a(n) _________.

3. A vibration or back-and-forth motion is known as a(n) ________.
oscillation
medium
vacuum
TODAY. All labs must be turned in by the end of the period. When you finish your lab, collect a review for the Tuesday's test and check your grades to see which papers you are missing. Any "MSG" or blank grades need to be turned in by the end of class TUESDAY.

Also, be sure to have your notebook organized and ready to be checked. Leave your notebooks in the back cabinets or with me before you leave class.
If you have not turned in the Wave Characteristics worksheet from last Thursday, turn that in today or tomorrow.
Warm Up 2/14
Your heart is beating at 60 bpm (beats per minute).
You see your crush/significant other across the room, and your heart rate increases by 10 bpm.
What are the new frequency and period of your heart beat? (convert min to sec)
Notebook Check Rubric

30 pts: Thermodynamics Notes
10 pts: Laws of TD Foldable
30 pts: Waves Notes
30 pts: Warm Ups 1/23, 27-30, 2/4-7, 10-14

Need to study vocab for the upcoming test?
http://quizlet.com/36031861/waves-flash-cards/
2/18-TEST
Find a seat at a desk, and clear it off except for something to write with. No more than two people to a lab table. By the end of today, any missing work must be turned in to receive credit for it.
I am currently in the process of checking notebooks, so yours might not be here today.
When you finish your test, make sure you have turned in any missing work.
There are extra credit crosswords at the front if you have no missing work to complete.
**Tomorrow, we will do an in-class writing assignment.
2/21
Updated grades are posted. The only things not included are the Wave Test Review and the In-Class Writing Assignment.
If you have a terrible notebook grade (or 2 missing daily grades) and want to improve it, write a 2-page essay on the importance of keeping up with your notebook as we go over notes in class. Or write a two page essay about the importance of doing the assignments and turning them in on time. If you are just missing one assignment, you can turn in a one-page essay.

Also, turn in restroom passes today!
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