Students will be working in pairs. Each pair needs:

- 1 index card with 2 slits cut in it (see image below)
- 4 strips of paper – take 1 sheet of paper oriented in landscape (horizontal) then cut it horizontally into 4 strips

In your pairs, set up your index card with one strip of paper like so:

Click here for the directions on PowerPoint PPT

(This is also a good time to check for understanding whether your students can distinguish between wave *frequency* and wave *speed* (velocity). Often, students lump the two together in the description, “it’s fast”.)

To check for understanding of the directions and to strengthen connection between vocabulary (wave speed and frequency) and concept, ask clarifying statements such as:

- “Who controls the wave
*speed*? The person moving the pen, or the person pulling the paper?” “Who controls the wave*frequency*? The person moving the pen, or the person pulling the paper?” - How might you
*increase*the wave*frequency*? - If the person pulls the paper faster, are they increasing wave
*speed*or wave*frequency*?

Avoid and discourage using terms like “fast” and “slow” *without* relating it to speed or frequency. A potential difficulty and point of confusion for students is distinguishing between speed and frequency (because both can be described as “fast” or “slow”), so help students distinguish the two by using them in context yourself and asking them to clarify if they describe something as “fast” or “slow” in isolation.

Example:

S: For this one, it was fast.

T: *What* was fast? There was a high *speed*, or high *frequency*?

S: ……………… um…………………………………………………………………. ………………………………………………………………………………. *[proper wait time]*

T: You moved your hand fast, or you moved the paper fast?

S: …………we moved our hand fast.

T: So that means high wave speed or high frequency?

S: …………………… high………….. frequency.

Students should end up with a total of 4 sets of waves on their 4 strips of paper.

Look at the two strips you labeled “Low frequency” and “High frequency”. Do they have the same wavelengths or different wavelengths? Which one has *shorter* wavelengths? Why? Would we say that the frequency of a wave and wavelength of a wave are *directly* proportional or *inversely *proportional?

Now, look at the two strips you labeled “Low speed” and “High speed”. Do they have the same wavelengths or different wavelengths? Which one has *longer* wavelengths? Why? Would we say that the speed of a wave and wavelength of a wave are *directly* proportional or *inversely *proportional?

How does this experiment relate to our wave equation, wavelength = velocity/frequency?

Objectives:

- Build
**fluency**with wave terms: speed (velocity) vs frequency - Understand the
**relationship**represented by the wave equation λ=v/f