movie to watch

link to explore sound/Fourier decomposition

I- INTRODUCTION: CONNECTION LAB PENDULUM WITH WAVES
1) REmember the pendulum ? This kind of motion is called harmonic motion. The cycle up - down - up repeats itself with the same period (time of a cycle), even if the motion is dumped. This kind of motion results from a restoring force (gravity pulling back the bob) and the principle of inertia (the bob wants to keep moving ). The same kind of motion can be produce using a mass moving up and down on a suspended spring.
REmember for an harmonic motion, the restoring force is proportional to _______________.

2) really advanced. calculus is needed or some help
A mass m, attached to a spring of constant K,  oscillates horizontally/ The recoiling force = - K x. K is the spring constant and x is the displacement of the mass (changes with time). Using F = ma find the differential equation that describes the motion.

3) So harmonic motion is the Nature response to a disturbance. A restoring force wants to bring back the system to equilibrium. These kind of systems are called oscillators. (obviously it oscillates, repeating the cycle over and over again). Imagine you have only one oscillator (let's say one pendulum). If the system is disturbed, the pendulum oscillates back and forth and it is as far as it goes. BUT If you connect oscillators together.
(Say you hang several pendulum on a horizontal string)
If you disturb the first pendulum, soon the others will start to oscillate as well.A disturbance in one, passes on to the next and continues down the line. This is the essence of mechanical wave.The wave is usually easier to see then the individual oscillator.



4) A wave is a disturbance that propagates from one place to another. Mechanical wave like sound wave, water wave, earthquakes, wave on a rope need a medium to propagate. For example, the water waves travel through ______, earthquake waves travel through ______, sound travel through ______ or _______. If the connection between one bit of matter and the other is weak, the wave is slow. (sound in air) but if the weak is strong, the wave is faster (sound in metal or in water). Or in other words, the speed depends on the recoiling force acting on every oscillator. The speed increases with the recoiling force and decreases with inertia.
For pendulum on a string, the recoiling force depends on _________, inertia is the ________
 

II VIDEO

Watch this video and answer the questions in class.

(email me if you were in my class for login and password)

I devided the questions in PARTS, following the linear progression of the movie.

PART I

1) (beginning of the movie)  give examples of waves :

2) The water waves in the ocean  are caused by _________________

3) The water wave carries energy? or water ? away from the source.

4) What are the 2 types of waves ? Write the definition for each of them.

5) What is the wavelength ?

6) What is the frequency ? Unit ?

7) AMplitude?

8) velocity of the wave ?        Velocity depends on the _______

PART I SOUND

1) sound are _____________ waves called _______________.
2) In a sound wave, what is moving back and forth or vibrate ?

3) do the tuning fork experiment. Dip a vibrating tuning fork in a glass og water.

4) The louder the noise the _________ the wave and so the larger the _____________ of the wave (frequency ? amplitude? wavelength?)

5) The higher the pitch the __________ the frequency of sound wave.

6) The human ear can hear from ____Hz to _______ Hz. Try the sound generator.
7) Dog can hear higher or lower frequency ? What about bats ? ______________

PART 3; speed of sound

8) The speed of sound depends on _____________. A student place a clock under a bell. The air is pumped out the bell. The clock rings. Can the student hear it ? ____________.
9)  speed of sound depends also on the ____________.

10) Why do you think, the Indians used to put their ears against the rails when checking on a train?

11) Why sound travels faster in water than in air?

PART IV: EM waves

12) It was thought before that light needs a _________ to travel. They called this medium ______________.

13) In an EM wave, what is wiggling ?

14) A EM wave is made of particle-wave. EM wave behaves like a wave when traveling in a vacuum but behaves like a  _________ when interacting with matter.

PART V interference

15) echoes occurs when ___________________----

16) On which principle the sonar is built ? _________________-

17) what is refraction?

18) diffraction? _______________________
Why can you hear behind corner ?

19) A ambulance arrives with a _____ pitch when it get closer to you but leaves with ________pitch  as it drives away. It is called he _______________.

20) What did  Edwin Hubble observed ? The ___  __________. As the Universe expands, other galaxies move away from us and their wavelength have been ______ stretched ? compressed? and their frequency (visible light)  __________ (decreases? increases ?) . The color is shifted toward the color _____. (low frequency color in the visible spectrum)
PART VI resonance, natural frequency

21) do the experiment with 2 tuning forks.

22) resonance results in an increase in amplitude. (U-tube Tacoma bridge, glass)

PART VII INTERFERENCE

23) interference occurs when waves ___________ in the same ___________.

24) When they meet, and pass each other if their amplitude add up, it is called a ________________ interference

25) When waves meet but partly or totally cancel each other, it is called __________________ interference.

26) When waves of the same frequency, traveling in opposite direction combine, they are called __________________.
(do experiment with slinky to find the standing wave)

27) In music, standing waves are called _________________________.

28) Can interference affect radio wave ? What happens then?

29) Let's take the quiz together.

QUIZ:
waves transport the energy of disturbances ?
The number of wave cycles in one second is called the wave ____________
The speed of the wave is called its__________
Sound waves are __________________ waves
Do longitudinal waves need a medium to transport the energy ?
The sound travels faster: in he air? in the ground?
Visible light is transported by__________ waves
The Doppler effect only applies to sound wave ? yes or no ?
Echoes or mirror images are examples of ___________waves?
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III- ANIMATIONS to illustrate what you just have learned

1) longitudinal vs transverse waves. click here

2) sound waves: click here

3) interference, waves can reinforce each other or cancel each other (partly and completely). click here        click here
very good animation

click image

click image

4) interference: standing waves. standing waves are called harmonics in Music:  click here     click here
http://www.kettering.edu/~drussell/Demos/superposition/superposition.html

excellent animations

5) interference with sound waves: beats (it happens when 2 waves with close frequency are added, the resulting frequency = difference between the 2 original frequency) . click here
http://www.falstad.com/mathphysics.html

 click image

6)When a system (crystal glass, suspended bridge, rope) is excited (voice, wind, resonance), the amplitude of the system keeps increasing. The glass can break and so can the bridge:
When a force is applied repeatedly at the natural frequency of any system, large amplitude oscillations result : click here

using resonance to break a wine glass
http://youtube.com/watch?v=17tqXgvCN0E

Tacoma bridge
http://youtube.com/watch?v=j5j20NSFNcg

7) Doppler effect, the wave is stretched or compressed/ If it is compressed (like a spring), you get a sonic boom
click here

click image

8) mechanical can move from one medium to another. The speed may change, depending on the medium inertia.
The frequency stays the same. The wavelength changes.  click here

Watch the waves traveling on a rope and passing through a boundary. Thinner (low inertia) to thicker rope (high inertia)

http://www.surendranath.org/Applets/Waves/TwaveRefTran/TwaveRefTranApplet.html

9) Any wave can spread around corner or after going through an  the opening  if the obstacle or opening  is smaller than
 the wavelength of the wave.

http://www.ngsir.netfirms.com/englishhtm/Diffraction2.htm

Sound wave have about 1meter wavelength , they will spread so you can hear behind a door.If  radio waves have the same dimension than a building, it will spread so you can detect them even behind the building.spreading = wavelength/ dimension of obstacle x distance you are.

To see an object, to take picture, to detect an object you can use different EM wave (visible light, Infra Red, micro wave, Xray) but the wavelength of the waves have to be significantly greater than the object you try to see. If not, the waves don't "see"the object. It pass through it without detecting it. That's why we use microwave in a radar. These waves are cms long and can see a plane. That's why the bats use ultra sounds with really small wavelengths that "can see"small bugs.

IV images to discuss (reference:  Conceptual Physics by Paul G. Hewitt, Addison-Wesley  )

click image and discuss

This blue glass let the blue wavelength to e transmittes. THe others colors can be absorbed ( increasing the temperature of the glass) and some can be reflected.	Sun light. We have more brightness in the greens and visible light. THat's why our eyes can only detect visible light. We evolved that way.	light transmitted by a piece of glass. From a particle point of view of light as quanta of energy, the quanta are absorbed and re emitted by the atoms of the glass. THat process slows down the light.
The waves will bend if the length of the obstacle is smaller than the wavelength of the waves. If this is not the case, a shadow is formed.	diffraction. water wave bending increases as the opening decreases.	EM spectrum. small wavelength = high frequency = high energy
polarization. polaroids can stop the light. Light is an electric field waving. THe first filter selects the electric fields oscillating up and down. The second one selects the side ways electric fields.		You can set a second tuning forks in resonnance as long as the frequency is the same.
light = waving electric field perpendicular to a magnetic field.	constructive or destructive interference.
using really small wavelength you can "see"or probe the atoms and molecules of atoms. You can use Xrays.