SOUND WAVES

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Contents

DATE


TOPIC


Sound Waves

CLASS


LESSON DURATION


2 periods

PREVIOUS KNOWLEDGE


Wave parameters, graphs, wave properties etc.

BEHAVIORAL OBJECTIVES


  1. Students would be able to describe how sound is propagated through a medium.
  2. Students would be able to describe what is pitch, Loudness and quality.
  3. Students would be able to use the speed of sound in echo calculations.

TEACHING RESOURCES


CRO, Synthesizer, connecting wires

INTRODUCTION


When a note is played by a flute and a violin, they sound different. How do these waves sound different and how do they travel from one place to another?

MATTER/CONTENT TEACHER ACTIVITY STUDENT ACTIVITY
Method of propagation A slinky is used to show that when one end is pushed the compression is propagated through the medium because of the elastic force. Inference is made of matter as bonds acts like strands of the slinky so when compression or rarefaction occurs, matter rearranges itself. For sound waves in air, the pressure redistributes the energy.2 The students are to help with making the inference as question are put to them as to how does matter resemble the slinky. They would take notes, and draw diagrams that the teacher puts on the board to render the concept visual.
Pitch, Quality, loudness The synthesizer is connected to the CRO and a note is played for different instruments, the students are then asked to determine the similarities and the differences in what is seen. A higher pitch is played for the same instrument and again they are ask for the similarities and the differences. They should note that the waveform is different but the period of the wave is the same.

For the second application, the waveform is the same except magnified but the period is different.

A definition of pitch, loudness and Quality is given with diagrams from the CRO screen The student copies diagrams and definitions
Speed of sound Students would be asked why if you are standing at the finish line of a 100m race why the athletes appear to sprint off before they hear the sound. Or why the sound of a pile driver does not correspond with the movement of the hammer. They are then given the typical value of the speed of sound. The students answers questions in discussion and take notes of how we can find the speed of sound in school.
row 5, cell 1 row 5, cell 2 row 5, cell 3


CLOSURE/ SUMMARY


The loudspeaker is drawn and used to illustrate how sound propagates and questions would be asked as to how the cone of the speaker moves in order to produce the particular quality, pitch and loudness.

EVALUATION


Homework questions would be given from the end of the chapter.

CONTINUATION


LESSON APPRAISAL (Self)

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