Teacher Guide. Including Student Activities. Module 5: Showing Wave Properties

Transcription

1 Teacher Guide Including Student Activities

2 ACTIVITY GUIDE Module 5: Showing Wave Properties Summary: All waves are rhythmic disturbances that carry energy through matter or space. These waves fall into two categories: electromagnetic or mechanical. For example, at a beach there are water waves, sound waves, and radio waves. If radio waves were not there, how could you listen to your favorite tunes while baking in the sun? Sometimes you even hear about earthquakes being described as seismic waves. Are these waves all the same? All waves are rhythmic disturbances that carry energy though matter or space. What we mean by rhythmic is that the waves repeat at regular intervals. When we talk about waves, we sometimes use the word propagate as a synonym for travel, and the word medium for the matter through which the wave travels. The first category, electromagnetic waves, is composed of changing electric and magnetic fields. Electromagnetic waves make possible radio or television broadcasts and microwave cooking. There are many other examples of electromagnetic waves, including X-rays and lasers. Changing electric charges also creates electromagnetic waves. Electromagnetic waves can travel through matter and space. The other category of wave is the mechanical wave. These waves need some kind of matter through which to travel; the matter can be solid, liquid, gas, or a combination of them. When a mechanical wave propagates through a medium, it is actually transferring energy from one place to another. It does this by making the particles of the medium bump into each other transferring energy from one particle to the next in a type of chain reaction. Objective: Demonstrate how the properties of a wave depend on the properties of the medium through which it travels. Recognize that electromagnetic waves can be propagated without a medium. When a wave propagates it transfers energy from one place to another. Module 5: Segment Length 14:23 minutes Page 2

3 Ohio Standards Connection: Grade Nine Physical Science Benchmark G: Organizer: Indicator 19: OSIC Demonstrate that waves (e.g., sound, seismic, water and light) have energy and waves can transfer energy when they interact with matter. Nature of Energy Show how the properties of a wave depend on the properties of the medium through which it travels. Recognize that electromagnetic waves can be propagated without a medium. Y2003.CSC.S03.G09-10.BG.L09.I19 Suggestions for the teacher: 1. Preview each segment before showing. 2. Prepare the class and gather all necessary materials. 3. Review segment content with class at each pause screen. 4. Begin lesson sequence activity after viewing lesson. Safety: Always be careful! Teachers and students should always exercise appropriate safety precautions and utilize appropriate laboratory safety procedures and equipment when working on science performance tasks. Page 3

4 Activity: Wave Properties In this activity students will identify the frequency, amplitude and phase of a wave, identify and explain the difference between a transverse and longitudinal wave, and relate the concept of vibration to frequency and pitch. Materials ring stand cone-shaped cup string Slinky springs and ropes (two meters long) shoe box rubber band paper clips coffee can matches ripple tank overhead projector paper straws crisp rice cereal can with top covered with a balloon salt piece of cloth baster Procedure: 1. Hang a cup with a hole in the bottom from a ring stand; fill it with salt. 2. Pull the cup and allow it to swing back and forth over construction paper. 3. Notice the straight line made by the salt streaming from the end of the cone. 4. Pull the construction paper along the table and let the pendulum continue to swing. Notice the formation of a wave made by the flowing salt. Have students form groups to experience activities on wave motion. Other activities: 1. Shout (do not blow) at the top of a can covered with a balloon with crisp rice cereal on top (vibration). 2. Pluck a rubber band which is lined with paper clips and stretched across a shoe box (transverse wave). 3. Hit a coffee can filled with smoke (longitudinal wave). 4. Use a Slinky, rope or springs to form longitudinal or transverse waves. 5. Make waves in a ripple tank placed on the overhead projector to produce circular waves (transverse wave). Place objects in the water to show that the wave moves, but the objects do not. Also, place a wooden block in the water to show incident and reflected waves. Page 4

5 6. Form a human wave by having ten people stand in a line, largest to smallest, with arms locked together, and pull the last person sideways (longitudinal wave). Then pull the last person forward (transverse wave). In both cases, the waves will be reflected back along the line. 7. Form standing waves by tying a rope to a fixed object and moving the rope up and down (incident and reflected wave). 8. Form a standing wave by connecting one end of a string to a timer and placing the other end over a pulley. Connect weights to the end of the string hanging over the pulley (170 gm). Show a wave in-phase and out-of-phase by using a rope. Have students put their fingers on the vibrating string to locate the nodes and see that the wave is out of phase. 9. Relate vibration to frequency and pitch of instruments. Slower vibration causes a lower pitch as shown by scratching a cloth slowly, then faster to get a higher pitch. a. Blow into a baster and notice the change in pitch caused by squeezing the end of the baster to change the level of water in the baster. b. Make a straw instrument by cutting the tip of the straw on each side and blowing into the straw while cutting the bottom of the straw at the same time. Notice the change in pitch. Page 5

6 Quiz: Wave Properties Substance dry air Speed of Sound Temperature Speed ( C) (m/s) Could the speed of sound be used to estimate dry air temperature, based on the data above? a) No, because the speed of sound in dry air is the same regardless of temperature. b) No, because as temperature increases, the speed of sound in dry air increases. c) Yes, because as temperature increases, the speed of sound in dry air increases. d) Yes, because as temperature decreases, the speed of sound in dry air increases. Page 6

7 Commentary: This multiple-choice question asks students to decide whether the speed of sound in dry air could be used to estimate the temperature of the air based on the given data. Students may recall that the properties of a wave, such as the speed of a sound wave, depend on the properties of the medium through which it travels. Students need to carefully observe and correctly analyze the information in the given data table. Answer choice C is correct. The given information shows that the speed of sound in dry air is dependent on the temperature of the air. As the air temperature increases, the speed of sound wave energy transfer through the dry air increases. A best-fit graph of these data could be used to estimate (interpolate) an unknown air temperature that corresponds to any speed of sound in dry air which falls within the range given in the data table. Answer choices A and D are incorrect. They represent inaccurate analyses and do not correctly describe how the speed of a sound wave in dry air depends on the air temperature based on the data table. Answer choice B is incorrect. While it correctly describes how the speed of a sound wave in dry air depends on the air temperature, it does not correctly analyze that the speed of sound in dry air could be used to estimate the temperature of the air from these data. Page 7

8 Ohio Content Provider Recommendations: Search String: transverse wave electromagnetic wave mechanical wave magnetic field Additional curricular resources can be found at the following websites using one or more of the search strings listed above to narrow your search. INFOhio Ohio Resource Center Ohio Department of Education Finding Additional Resources Using: D3A2 The D3A2 helps educators analyze data, and points them to resources such as lesson plans, assessments and activities designed specifically to address the academic need identified by the data. In addition to linking content to data analysis, educators will have general search capabilities to locate education content resources aligned to the Ohio s Academic Content Standards. Sample D3A2 Standard Search Results: Light1: Light Making Light of Science: Retrieved from the Ohio Resource Center o Page 8