Mehmet Demirtas 08 18 2008 Inexpensive 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 demirtas bascs org Abstract 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 MacIsaac 1 Literature There is much literature which discusses how to teach waves This paper will review some 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 Some Representative 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 the motion 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 the two 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 experiment is 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 with sticky 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 3 intervals 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 prepackaged kit available for students to determine the velocity of the sound An alternative to purchasing the kit is to make your own from easily available materials The purpose of this experiment is to determine the velocity of the sound by using resonance The apparatus operates
View Full Document
Unlocking...