Monday, Nov 15, 2010

Handed out 3 Tiger Passes and stamped them.
Hand back and go over midterm.

Made sure students had Quia website, username, and password.

www.quia.com/profiles/rholmes100

More emphasis on Quia this quarter
There will be Quia assignments for homework after every class.
There will be quizzes to start classes
Students need to bring their covered textbooks to class.

New Topic - Waves and Sound

Vocabulary: wave, transverse wave, longitudinal wave, period, wavelength, frequency, speed of the wave, crest, trough, amplitude, compression, rarefaction

Showed pictures of energy cards for radiation and sound

Energy cards: This form of energy is noisy ________ sound
This is how energy gets from the Sun to the Earth ______ radiation (light)

These are both green cards meaning energy is doing something, it is being transferred, it is moving from one place to another (remember, blue cards show stored energy).

How does that energy move?

Students stood up, sat down and wave went around the room.
Look at that! People moved up and down, but disturbance went side to side. In a wave, particles, in this case the people, stay pretty much in one spot but the wave, or disturbance, can travel far away.

Energy moves in waves.

If I want to get your attention, I could walk up to you and tap you on the shoulder. I could also throw a ball at you and when it hit you you would turn around. Or...I could say, "Hi". In the first two cases, something material traveled from me to you, either me or the ball. In the second case, energy moved in a wave. When I spoke, I jiggled the air molecules near my mouth which hit other air molecules near them and so on until they jiggled air molecules near your ear. The air molecules near my mouth were NOT the same that jiggled your ear. The energy moved in a wave.

Content objective - students will be able to describe a wave. A disturbance carrying energy without anything material traveling from one place to another.

Didn't do *****************************
Demonstrated how sound worked by lining up students. A push on a person at one end caused a push on the next and so on. The pushes were side to side and the disturbance traveled side to side. The person at one end did NOT go to the other end. This kind of wave in which the motion of the particles, in this case people atoms, is side-to-side and the wave travels along in the same direction is called a longitudinal wave. The wave travels a-long the same direction as the motion of the particles. This is how sound travels.

In their notebooks, students sketched the row of people and showed the side to side motion. They labeled this as "longitudinal wave" and wrote down "sound" as an example.

Next the students raised and lowered their arms. This time the motion was up and down but the wave traveled side-to-side. I demonstrated the two directions with my arms. If the arms are at 90 degrees, the two motions are perpendicular. A wave in which the motion of the individual particles (people atoms) is up and down but the wave moves perpendicular to this (side-to-side) is called a transverse wave. An example is light.
************************End of did not do

The up and down motion is a wiggle or vibration. If the wiggle moves, we get a wave. Showed on whiteboard. Up and down, and then moving side to side made a wave shape. There are ups and downs and the pattern repeats.

The time it takes my hand to move up and down once is the period of time, or period, measured in seconds. It is the time for one wiggle.

In that period of time, the wave has moved one basic unit of the repeating pattern. This basic unit is called the wavelength. The disturbance has returned back to the same distance from the equilibrium point and is moving in the same direction.

From our study of motion, we know that speed = distance/time. Here the distance is a wavelength and the time is the period.

Suppose we have something that wiggles like this pendulum. It takes 1/4 seconds for it to swing back and forth. The period is 1/4 seconds. How many times does it swing back and forth in 1 second, or how frequently does it swing back and forth? 4 times a second. The number of repetitions in one second, or how frequently the motion repeats, is called the frequency. The frequency is measured in repetitions/sec. This unit is also called Hertz or Hz.

A high frequency has high Hertz. Demonstrate with singing rod. The higher the frequency, the more it hertz "hurts" your ears.

The distance between one peak to the next is the wavelength. The wavelength is the distance between two identical points on the wave. The high points of a transverse wave are called the crests (just like the crest of a water wave) and the low points are called troughs. Horses used to drink out of basins called troughs.

Slinky demo. Moving hand back and forth sets up a transverse wave in the slinky. If you do something often, we say you do it frequently. If you move your hand back and forth quickly, you move with high frequency. If you move back and forth slowly, your frequency is low. A high frequency motion sets up a wave in which the peaks are close together, the wavelength is short. A low frequency motion sets up a long lazy wave - long wavelength with the peaks far apart. The volume control is also called an amplifier. The size of the wave, how big it gets from the center position is called the amplitude. We generated several waves varying the amplitude, frequency. If you move with high frequency or high amplitude or both, it takes more energy.

High frequency = high energy = short wavelength
Low frequency = low energy = long wavelength
High amplitude = higher energy

See if we can read the equation: speed = wavelength * frequency
For the same speed, if the wavelength is big (long wavelength), the frequency is small (low frequency)
For the same speed, if the wavelength is small (short wavelength), the frequency is big (high frequency)

Generated longitudinal waves in slinky. Showed that in some places the coils were close and in others they were spread apart. Sketched this pattern on the board. The parts were the coils are close or compressed are called compressions. The parts where they are far apart or "rare" are called rarefactions.

We generated several types of longitudinal waves varying the frequency and amplitude and observing the wavelength.

Content objective: Students will be able to describe using examples the differences between longitudinal and transverse waves and give examples of each.

Content objective: Students will be able to identify the features of longitudinal and transverse waves on a diagram.

Content objective: Students will be able to explain the relationship between frequency, energy, and wavelength of a wave.

Short wavelength, higher frequency, more Hertz (hurts). Demonstrated singing rods. Again, longer rod produces lower pitch and longer wavelength. Students found this painful. (Lots of hurts)

Oscilloscope demo. Long wavelengths have low frequency and low pitch.
Higher frequency means shorter wavelength and higher pitch. Made many annoying sounds.

Didn't do microphone**********
Hooked up microphone and checked whistles and o's and e's for frequency and pitch and wavelength. Spoke into microphone and saw voice print.
************

Long wavelength, low frequency, low pitch.

Showed pull-a-tune xylophone. Longer bar produces lower pitch, longer wavelength.

Demonstrated straw duck calls. Longer straw produces lower pitch, longer wavelength.
Students made duck calls.

Finished by stamping students notebooks with tornado stamp

There are some quia activities involving wave vocabulary that they should look at.
Assigned Quia Quiz- Waves Physical Science - Day 1
Quia Activities - Waves Vocab, Waves Vocab 2