Properties of Waves

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SWBAT identify that all waves have amplitude and frequency.

Big Idea

In this direct instruction lesson, students draw sketches in their science notebooks in order to make sense of wave properties.

Engage and Explain

20 minutes

I begin this lesson by reminding students that waves are the way energy moves from place to place. Sound moves from a mouth to an ear by waves. Light moves from a light bulb to a book page to your eyes by waves. Waves are everywhere.  I tell students that they are are surrounded by radio waves, television waves, cell phone waves, light waves, sound waves and more.  Next I tell students that waves come from vibrating particles and are made up of vibrating particles. 

Next I show this wave properties presentation. properties of waves presentation

As I present each slide I use direct instruction to help clear up any misunderstandings or confusing points. 


30 minutes

Next, I instruct students to write the word amplitude in their science notebooks. I direct students to write a "kid friendly" definition of what amplitude means.  After most students have a definition written I remind students that amplitude is the height of a wave from rest position. The higher the amplitude, the higher the wave. Also, the higher the amplitude the higher the energy of the wave.

 You can see in this photograph, a student writes that amplitude is the "height of the wave from rest position."  The student goes on to write that ocean waves are big waves that will knock you down, lake waves will not knock you down.  This student is definitely making sense for him/herself about wave amplitude. 


I lead a brief discussion about waves that have a high amplitude and how the particles in the wave move. For a wave to have a high amplitude the particle has to be moving over a large distance (large being a relative term here, the distance may still be miniscule). The more the particle moves, the more work there is being done on the particle (work is force and distance). The more work there is, the more energy there is and so, a wave with a large amplitude has more energy than a wave with a small amplitude.

I tell students that if they've ever been in the ocean this may be more clear. Small little waves don’t have the energy to knock you over, but the larger out! In sound, amplitude determines the loudness of the sound. In light, amplitude determines the brightness.

 I show students these two photographs and ask them to think about the difference between amplitude and wavelength. 



I lead a similar discussion for wavelength. Students copy the word wavelength in their notebooks and write the definition.  When most students have finished writing a "kid friendly" definition, I remind students that wavelength is the distance between two like parts of the wave. In other words, the wavelength is the distance between two high parts (hills) of the wave. Or it’s the distance between two low parts (troughs) of the wave. 

Notice in this student sample that the student does not remember that the top of the wave is called the crest.  This student notes the tops as "hills." 


For the remainder of the lesson, students use a piece of paper (to be attached in their science notebooks later) to draw a picture that will help them remember what wave amplitude and frequency are. I let students be creative with their pictures, just like the photograph above. 



10 minutes

I use the student drawings to informally evaluate if students understand the difference between wavelength and amplitude.  When I am deciding, I make two piles.  One pile shows student work that I can tell clearly depicts understanding, while the second pile is student work that doesn't show that a student knows the difference between wavelength and wave amplitude.  

 You can see in these photographs examples of student drawings.  This particular drawing shows amplitude on the left and wavelength on the right.  The student has marked on the drawing to show crest to crest as wavelength and made marks from rest position to the height of the wave for amplitude. 



 It is unclear if this student realized that amplitude and frequency are different.  The amplitude drawing could also be used to show frequency.  


 This student uses an ocean theme to showcase amplitude and wavelength.  The student's drawing seems to depict that he/she understands the difference. 


This student's drawing is very clearly showing that he/she understands the difference  between amplitude and wavelength.