Waves
Learning objectives
I can use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling in various media
I can evaluate the claims, evidence, and reasoning behind the idea that electromagnetic radiation can be described either by a wave model or a particle model, and that for some situations one model is more useful than the other.
Success Criteria
�
Clifton Bluhm
NATIONAL GEOGRAPHIC – Earth Report 2009
Take your time watching the video and answer the questions below it.
Video : https://www.youtube.com/watch?v=KWzyQKcJBYg
Differentiated Task: |
1. In your words, describe the wave. |
2. What is the wavelength? |
3. what will happen to the amplitude of a wave if the energy increases ? |
4. How frequency and velocity are similar ? |
5. Analyze the relationship between frequency and wavelength |
6. Create an equation to find the relationship between V, ƛ and f |
Water Wave
http://7art-screensavers.com/screenshots/Wave/attracting-wave.jpg
The bottom of the wave “drags” against the shore, and the top of the wave falls over.
Low�Pressure
Low�Pressure
Fast
Fast
Bernoulli’s Principle
What makes waves?
Bernoulli’s Principle
What makes waves?
NATIONAL GEOGRAPHIC – Earth Report 2009
http://www.kettering.edu/%7Edrussell/Demos/rad2/mdq.html
Propagation ≡
The process of spreading out into a larger area.
The process by which electromagnetic waves or sound waves are transmitted through a medium.
Medium ≡ The material the wave moves through
What is the difference between the two waves ??
Longitudinal Wave
Transverse Wave
Particles in the medium vibrate PERPENDICULAR to the wave motion.
Particles in the medium vibrate PARALLEL to the wave motion.
Wave Motion
`
Wave Motion
Wavelength
Crest
Crest
Trough
Trough
Wavelength
Wavelength
Amplitude
Amplitude
Transverse Wave
Exploratorium, San Francisco – Clifton Bluhm
http://catalinaphysics.freeservers.com/photo.html
Wavelength
Compression
Wavelength
Rarefaction
Longitudinal Wave
Large Amplitude
= Wavelength
(meters)
Wavelength
λ
λ
λ = Wavelength
= 4.3 cm
λ = Wavelength
= 17.1 cm
PERIOD ≡
seconds�wave
The time it takes for one wave to pass. (one complete cycle)
FREQUENCY ≡ The number of waves that pass a given point each second.
waves�second
(Hertz)
f = 1 Hz
Frequency =
waves seconds
Period =
seconds�wave
Period =
1�Frequency
Frequency =
1�Period
Period = 10 seconds
Frequency = 0.1 Hertz
Period = .02 seconds
Frequency = 50 Hertz
Transverse Wave
FREQUENCY ≡ The number of waves that pass a given point each second.
(1 Hertz)
wave�second
1
Longitudinal Wave
FREQUENCY ≡ The number of waves that pass a given point each second.
(1 Hertz)
wave�second
1
Frequency = ?
Period = ?
2 Hz
.5 s
Frequency = ?
Period = ?
1 Hz
1 s
Frequency = ?
Period = ?
6 Hz
.167 s
Time slowed down
Frequency = ?
Period = ?
.33 Hz
3 s
23 cars in 16.5 seconds = 1.4 cars/second
Each car is 10.5 meters long.
1.4
cars�second
· 10.5
meters�car
= 14.7
meters�second
How fast is the train moving?
Velocity = Frequency · Wavelength
v = f · λ
λ
waves�second
meters�wave
.
v = f · λ
The velocity�(for a given type of wave�and a specific medium)�is constant!
FREQUENCY�is inversely proportional to�WAVELENGTH
v = f · λ
f = 4 Hz
f = 1 Hz
λ = ¼ m
λ = 1 m
http://www.eliblack.com/pix/photos/edited/edited05.jpg
λ = 2.5 cm
Three waves go by the pencil every second. ( f = 3 Hz )
Find the wave velocity!
FM�(Frequency Modulated)
AM�(Amplitude Modulated)
http://en.wikipedia.org/wiki/Image:Amplitude-modulation.png
?
http://ceoworld.biz/ceo/wp-content/uploads/2009/11/barcode.png
http://www.1055jackfm.com/
frequency = 97.3 MHz
(97,300,000 Hz)
What is the wavelength of the signal?
Velocitylight = 3 x 108 m/s = 300,000,000 m/s
v = f · λ
λ = 3.08 meters
megahertz
UNITS?
What variables affect the velocity of a wave on a string?
How does each variable affect velocity?
Wave�Interference
Matter cannot pass through matter and�immerge on the other side UNEFFECTED
http://www.shmcc.co.uk/forum/viewtopic.php?t=8742
ENERGY CAN!
http://radio.weblogs.com/0137829/2004/05/28.html
What part of a wave contains�the ENERGY of the wave?
The AMPLITUDE
+5 + (+2) = +7
+5 + (-2) = +3
-5 + (+2) = -3
-5 + (-2) = -7
Adding Positive and Negative Numbers
NEGATIVE
POSITIVE
Add the BLUE wave to the RED wave.
Bluhm
Bluhm
First
Fourth
Third
Second
Now you try!�Come up to the board!
Check your work!
Double slit experiment
Electron -Double slit experiment
I can . . .
�