Mehmet Demirtas 08.18.2008Inexpensive Activities and Resources for Teaching High School Waves and Sound Mehmet Demirtas, Department of Physics, State University of New York – Buffalo State College, 1300 Elmwood Ave, Buffalo, NY 14222 [email protected]: This paper reviews the wave concept, including both articles and web sites helpful in teaching New York State High School students. There are useful activities, instructions and experiments from different sources. The purpose of one of the article is to share with teachers and other educators the use of the strategies to change preconceptions as applied to physical science topics, like waves, which are difficult for students to understand. Other articles include activities to observe wave motion, and to investigate the relationship among wave speed, wavelength and frequency. Teachers can find questions about waves with real-life applications. There is an activity that one can use to investigate transverse waves using sticky tape and straws. A lab is included to study speed of sound and resonance. This paper also includes websites having simulations and animations that make it easier for the students to understand the concept. One link contains animations which visualize certain concepts concerning acoustics and vibration. Through other websites one can watch a string vibrate in slow motion, wiggle the end of the string to make waves, or adjust the frequency and amplitude of an oscillator. Acknowledgement: This manuscript was prepared in partial fulfillment of requirements for PHY690: Masters Project at SUNY – Buffalo State College under the guidance of Dan MacIsaac1Literature: There is much literature which discusses how to teach waves. This paper will reviewsome of the literature and present ideas for low cost implementation in the classroom. Where applicable the New York State Learning Standard will be noted. One of the difficulties with learning physics is replacing old understanding with new. As instructors we need to be aware of students’ preconceptions so that we can bring them to the forefront, under conditions in which they fail utterly to explain something that is of sufficient importance to the student that the student will be forced to abandon the prior understanding. In his work on Targeting Students’ Science Misconceptions, Joseph Stepans gives a list of “SomeRepresentative Student Misconceptions about Waves- Students often think of frequency in terms of time units and confuse it with period.- The motion of the medium, up and down for water waves, is frequently confused with themotion of the wave itself, outward from a pebble dropped in a calm pool.- Students often confuse the independent aspects of waves-primarily amplitude, frequency, and velocity-into just two parts, the motion of the medium and the overall intensity. For example, a common belief is that a rapid oscillation ensures a large amplitude and fast velocity. Or, conversely, small amplitude implies a slow velocity.- Wave collisions, according to the intuition of many students, result in the permanent cancellation of both waves, as if they were mechanical objects.”(page 174)In the same book, the author suggests that the “Sources of Students’ Confusion and Misconceptions are:- The relationship between frequency and period requires an understanding of ratios, which is difficult concept of many students.2- It is possible to acquire and use all of the wave vocabulary without gaining much understanding of waves themselves. Often, use of the words is essentially all that is tested.- Wave motion is a cumulative phenomenon of much local motion. The distinction between thetwo is a subtle one, but one that is crucial for understanding.”(page 175)In the work on String and Sticky Tape Experiments, R. D. Edge suggests two activities to observe wave characteristics. To explain the first activity he says that “The aim of the experimentis to construct a device along which longitudinal waves travel slowly, so that the motion may be followed in detail. Connect sixteen paper clips in a string using sixteen rubber bands, to provide a weak restoring force. To slow the longitudinal wave, attach two marbles to each paper clip withsticky tape. Now, attach both ends to a firm-anchor – you can fasten one end to your desk and hold the other with your left hand. With your right, pull back the last the top of a doorway or some other suitable point. A little tension should be provided at the bottom end. Watch the compressive pulse travel along and be reflected. Then, if you move the marble away from your left hand before releasing, you get a rarefaction traveling down the system. To examine what happens if we have an open organ pipe, attach three or four rubber bands without marbles or paper clips between the far end of the string and the table.”(page 1-2) In the second activity students will observe transverse waves by producing pulses reflected from both free and fixed ends, and they will study standing waves. Materials include sticky-tape, about two dozen drinking straws and paper clips. To perform the activity, R. D. Edge tells to “Attach one end of the tape to the table top, pull about two feet off and let it hang down. Place one paper clip in each end of each drinking straw. Stick the center of the straws at one inch 3intervals along the sticky tape, until you have about 24 of them attached. Now, looking end on at the straws, pull the tape reel, to make the strip taut, and give the bottom straw a tap. You will see a transverse wave pulse travel up the strip, and be reflected at the top. You may induce standing waves by rotating the bottom straw too and fro with the right period. If you unreel a length of tape, you may study reflection from a free end, just as you did reflection from a fixed end. For the last foot or so of the tape, put two paper clips at each end. Now you can study the reflection of a wave traveling from a less dense to a denser medium (top of the bottom) or vice versa (bottom to top). Note how, in each case, part of the wave is reflected at the intersection; but in one case it changes sign (phase) and in the other case it does not.”(page 1-3) I tried this activity in my Regents Physics class with much success. The students enjoyed the activity and directly observed the desired wave characteristics. There is a
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