What is Sound?
When sound travels through the air, air molecules get squeezed together and, in turn, squeeze the air molecules next to them. In a domino-like effect, a pulse of compression called a “sound wave” travels through the air.
Set out materials
Tables of 4-6 students
Slinky toys (1 per table)
Graph paper and pens
In this activity students are to make longitudinal waves by moving the ends of the Slinky in and out.
Running the Activity
In this activity, students will create and experience longitudinal pressure waves using Slinky toys. Place the Slinky toy laying on its side on a tabletop. Have students take turns being the “fixed end” and the “moving end” of the Slinky. The person who is the fixed end simply holds the Slinky with a hand cupped over the open end. The person who is the moving end holds the opposite end of the Slinky and rapidly moves their end in and out towards and away from the fixed end.
Observe and do
What does the fixed end feel like when the moving end moves back and forth quickly versus slowly? Can you identify the areas of compression in the Slinky? Are there more areas of compression when the moving end moves quickly? How many areas of compression did you count when the moving end went in and out quickly? How many areas of compression did you count when the moving end moved in and out slowly?
What’s going on
When the moving end of the Slinky moves in and out a segment of the Slinky gets “compressed” or squeezed together. This compression creates a pressure wave that travels down the length of the Slinky until it reaches the fixed end. The same thing happens when sounds are made and travel through the air, except with sound, air molecules are compressed instead of the Slinky.
A PDF VERSION OF THIS LESSON CAN BE FOUND HERE
We encourage teachers to use and alter these lesson plans. But, don’t be shy! Please let us know what you do and send us photos, videos, or notes. We’d love to hear from you. firstname.lastname@example.org