A Wave of Cooperation

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Amberly Wilkinson
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1 A Wave of Cooperation The students will peer teach in cooperative learning groups some basic topics regarding waves. Materials: Student sheets Note sheets Procedure: 1. Place students into home teams of four per team to participate in a cooperative learning jigsaw activity. 2. Assign students in the home teams a number for expert assignment s from Have students move to expert groups, students with the same numbers, to study and peer teach the information provided on the Student Sheet. 4. Once students are experts on their topics, have them return to their original groups to peer teach members of their home teams. 5. Students will complete information on their note sheets as they peer teach in their groups. 1

2 WAVELENGTH In the diagram the straight line represents the position of the medium when no wave is present. This medium could be imagined as a rope fixed at one end a few feet above the ground and held by you at the other end. The straight line represents the position of the medium as a wave travels through it. We simply say that the curved line is the wave. If we consider the rope mentioned before, this wave could be created by vertically shaking the end of the rope. Often, when several waves are traveling along a medium as shown above, the continuous group of waves is called a wave train. The wavelength is the distance from two positions on the wave that are identical and adjacent. They are often measured from top to top or bottom to bottom, but they can be measured at any location as indicated by the middle wavelength line. Wavelengths of light are measured in meters, and more specifically, wavelengths of visible light are measured in nanometers (nm). 1 nanometer = 1x10-9 meters 2

3 WAVE COMPONENTS In the diagram the straight line represents the position of the medium when no wave is present. This medium could be imagined as a rope fixed at one end a few feet above the ground and held by you at the other end. The straight line represents the position of the medium as a wave travels through it. We simply say that the curved line is the wave. If we consider the rope mentioned before, this wave could be created by vertically shaking the end of the rope. Often, when several waves are traveling along a medium as shown above, the continuous group of waves is called a wave train. The top or peak of the wavelength is crest and the lower valley is the trough. The amplitude is the amount of displacement from the medium. It is from rest to crest. In sound waves, the amplitude is greater in a loud sound and less in a quieter sound. 3

4 FREQUENCY In the diagram the straight line represents the position of the medium when no wave is present. This medium could be imagined as a rope fixed at one end a few feet above the ground and held by you at the other end. The straight line represents the position of the medium as a wave travels through it. We simply say that the curved line is the wave. If we consider the rope mentioned before, this wave could be created by vertically shaking the end of the rope. Often, when several waves are traveling along a medium as shown above, the continuous group of waves is called a wave train. Frequency refers to how many waves are made per time interval. If the drawing below shows waves in motion from left to right, the number of waves passing a given point per second indicates the frequency. This is usually described as how many waves are made per second, or as cycles per second. The top wave has a higher frequency as more wavelengths will pass per second. If ten waves are made per second, then the frequency is said to be ten cycles per second, written as 10 cps. We use the term Hertz to state frequency. 1 cps = 1 Hertz = 1 Hz 4

5 SOUND WAVES Sound waves are mechanical waves that require a medium to transport their energy, so they do not travel in a vacuum. Air is an example of a medium. The medium is displaced, but it then returns to equilibrium. When a sound travels through the air, the air does not go with the sound, it only provides a medium for the sound to travel. Sound waves are longitudinal waves, waves that displace the particles of the medium in a direction that is parallel to the direction of the energy flow. Longitudinal Wave LIGHT WAVES Light waves are electromagnetic waves that can travel through matter as well as a vacuum. They are produced by vibrating electrical charges and do not require matter for an energy transport. Electromagnetic waves are transverse waves and travel in a direction that is perpendicular to the direction of the energy flow. Transverse Wave 5

6 NAME THAT SOUND Materials: (per team of 4 students) Set of 6 sound cards Procedure: 1. Have students listen to different sounds and select the card that shows the sound. 2. For each card, have students record the justification for the selection on the chart below. 3. Once all sounds are determined, have students check with peers to verify their choices. 4. As a class, discuss the correct answers for the examples given and the information on each card. Sounds Letter Characteristics

7 KEY Medium loud and high-pitched Loud and low pitched Medium loud and medium pitched Soft and low pitched Loud and high pitched Soft and high-pitched 7

8 ROLE PLAY Materials: Task card for each team Procedure: 1. Divide the class into 3 groups to role play as a team a model of the light indicated on their card. (Include more students in the Unpolarized Light group as they will need several students to represent different wavelengths in different planes.) 2. Allow students minutes to decide on their strategy to demonstrate the properties described. 3. Assess the students on applying information learned in previous activities regarding the card description. (Example: a wavelength has crests and troughs) 4. Have students demonstrate their model for the class. Task Observed Yes No Unpolarized Light Polarized Light Different wavelengths for different colors of light; light traveling in different directions to represent different planes Different wavelengths for different colors of light; Light traveling in one plane Laser Light The same wavelength for the same color of light; Light traveling in one plane 8

9 Task Cards UNPOLARIZED LIGHT The electromagnetic waves vibrate in a variety of directions and in different planes. Light is made of different colors, and thus, different wavelengths. POLARIZED LIGHT The electromagnetic waves vibrate in one plane. Light is made of different colors, and thus, different wavelengths. LASER LIGHT The electromagnet waves vibrate in one plane. Laser light is made of one wavelength. 9

10 Absorb, Reflect or Transmit? Imagine that electrons are connected to atoms by springs. The electrons of the atoms will vibrate at a natural frequency. The frequencies differ for elements. Light particles also vibrate at a natural frequency. As light waves strike matter (made of atoms), the light will be absorbed, transmitted or reflected. Light waves that have the same natural frequency as atoms making up an object will be absorbed, and they will set the electrons of the atoms into vibration at their natural frequency. The energy will then be changed to heat energy. Light waves that do not have the same natural frequency will be transmitted or reflected. Light is transmitted if the object is transparent and reflected if it is opaque. What determines the following: Light is absorbed? reflected? transmitted? The electrons that have the same frequency as the light are set into motion. This is an example of resonance--one object causes another object to vibrate because they have the same natural frequency. 10

11 Building a Spectroscope Students will construct a spectroscope to demonstrate how light bends. Materials: (per student) Toilet tissue tube Markers Diffraction grating Scissors Index card Pencil Electrical tape Packing tape Ruler Procedure: 1. Trace the end of the toilet tissue tube onto the index card and cut out the circle. 2. Cut a small square (~1.5 cm 2 ) or a small circle (~1.5 cm diameter) in the center of your circle made from the index card. 3. Place a piece of diffraction grating (slightly larger than the hole) over the hole. Tape the edges of the diffraction grating down with electrical tape. Do not tape over the center of the diffraction grating (you will look through this opening). 4. Place the cut-out circle on one end of the tube and secure it with electrical tape. 5. Cover the opposite end of the tube with electrical tape allowing for an opening in the center, measuring 1 mm and 1 cm long. This slit will allow the light into the tube. 6. Cover other holes or spaces with electrical tape to prevent light pollution. 7. Decorate your tube with a spectrum or other colorful images. 8. Cover the entire tube with packing tape for added protection. 9. Point the spectroscope at the lights and look through the end with diffraction grating. You should see a spectrum. 10. Look at different lights with your spectroscope to compare the patterns you observe. How does it work? Diffraction grating is a film with thousands of fine, parallel slits. As light travels to the film, it runs into obstacles and bends to pass through the grooves. The light spreads around the edges of the obstacle or defracts. As the light bends, it separates into its different wavelengths and a spectrum is visible. Activity adapted from Suzy Dunnum, Tahoka Hr. High School, 8 th grade 11

12 Building a Kaleidoscope Students will construct a kaleidoscope to demonstrate how light bends. Materials: 2 Dixie cups Polarizing film Transparent tape (glossy) Scissors Procedure: 1. Cut the bottom from two Dixie cups. 2. Tape a piece of polarizing film onto the end of each cup. 3. Tape over the polarizing film on each cup with numerous pieces of tape in random patterns (more tape and a more random placement makes for a better kaleidoscope!). 4. Slip one cup inside the other cup and look to the light through the open end as you twist the cups. Observe the spectacular display of color! How does it work? Polarized light travels through the tape at different speeds, resulting in different colors. The light travels at different speeds because of the alignment of the molecules in the tape. The molecules run parallel to the length of the tape, and polarized light that passes through the tape parallel to these molecules will move slower than molecules that pass through the tape perpendicular to the molecules. The result is polarized light traveling at two different speeds, so double refraction occurs. Activity adapted from Suzy Dunnum, Tahoka Hr. High School, 8 th grade 12

13 LIGHT From Wikipedia, the free encyclopedia. Physics of Color The colors of the visible light spectrum. color wavelength interval frequency interval red ~ nm ~ THz orange ~ nm ~ THz yellow ~ nm ~ THz green ~ nm ~ THz cyan ~ nm ~ THz blue ~ nm ~ THz violet ~ nm ~ THz Electromagnetic radiation is a mixture of radiation of different wavelengths and intensities. When this radiation has a wavelength inside the human visibility range (approximately from 380 nm to 740 nm), it is called light. The light's spectrum records each wavelength's intensity. A surface that diffusely reflects all wavelengths equally is perceived as white, while a dull black surface absorbs all wavelengths and does not reflect. The frequencies are approximations and given in terahertz (THz). The wavelengths of visible light, valid in vacuum, are given in nanometers (nm). The intensity of a spectral color may alter its perception considerably; for example, a low-intensity orange-yellow is brown, and a low-intensity yellow-green is olive- 13

2. Allow students minutes to decide on their strategy to demonstrate the properties described.

2. Allow students minutes to decide on their strategy to demonstrate the properties described. ROLE PLAY Materials: Task card for each team Procedure: 1. Divide the class into 3 groups to role play as a team a model of the light indicated on their card. (Include more students in the Unpolarized