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Chapter 5: Waves

Doing the Wave

When an earthquake occurs, the waves of energy are recorded at points all over the world by instruments called seismographs. By comparing the data that they collected from their seismographs, scientists discovered that the interior of Earth must be made of layers of different materials. How did the seismographs tell them that Earth is not the same medium all the way through?

 
Recognize the Problem

Can the speed of a wave be used to identify the medium through which it travels?

 

Form a Hypothesis

Think about what you know about the relationship between the frequency, wavelength, and speed of a wave in a medium. Make a hypothesis about how you can measure the speed of a wave within a medium and use that information to identify an unknown medium.

     Goals

  • Measure the speed of a wave within a coiled spring toy.

  • Predict whether the speed you measured will be different in other types of coiled spring toys.


    Data Sources
Test Your Hypothesis

     Plan

  1. Make a data table in your Science Journal like the one shown.

  2. Write a detailed description of the coiled spring toy you are going to use. Be sure to include its mass and diameter, the width of a coil, and what it is made of.

  3. Decide as a group how you will measure the frequency and length of waves in the spring toy. What are your variables? Which variables must be controlled? What variable do you want to measure?

  4. Repeat your experiment three times.

 

     Do

  1. Make sure your teacher approves your plan before you begin.

  2. Carry out the experiment as you have planned.

  3. While you are doing the experiment, record your observations and measurements in your data table.

Analyze Your Data
  1. Calculate the frequency of the waves by dividing the number of vibrations you timed by the number of seconds you timed them. Record your results in your data table.

  2. Use the following formula to calculate the speed of a wave in each trial.

    wavelength x wave frequency = wave speed

  3. Average the wave speeds from your trials to determine the speed of a wave in your coiled spring toy.

Draw Comclusions
  1. Post the description of your coiled spring toy and your results using the form below.

  2. Compare and contrast your results with the results of other students.

  3. How does the type of coiled spring toy and the length it was stretched affect the wave speed? Was your hypothesis supported?

  4. Would it make a difference if an earthquake wave were transmitted through Earth's solid mantle or the molten core?

 

Post Your Data

Results
Trial
Length spring was stretched (m)
Number of crests
Wavelength (m)
Number of vibrations timed
Number of seconds vibrations were timed (s)
Wave speed (m/s)
Trial
Length spring was stretched (m)
Number of crests
Wavelength (m)
Number of vibrations timed
Number of seconds vibrations were timed (s)
Wave speed (m/s)
Trial
Length spring was stretched (m)
Number of crests
Wavelength (m)
Number of vibrations timed
Number of seconds vibrations were timed (s)
Wave speed (m/s)
* First Name:
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* School:
 

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