Waves aren’t just for the ocean, pal. They’re everywhere: soundwaves and radio waves, microwaves (not just the kitchen device but the energy it emits), even light travels in waves. Their basic motion (sort of a “wave” kind of motion) makes them similar; what makes them different is the direction of that motion. Up and down, back and forth, parallel, perpendicular—waves got moves like you’ve never seen before!
The motion of a specific type of wave is set: a soundwave will move like a soundwave no matter what. The medium through which a wave passes, however, can affect the force of the wave and alter its effects. To better explain this motion notion to your students, we offer this quick and easy Demo Science experiment.
Wavy Gravy & His Best Friend Davy
The only supplies you need for this science demo are something your classroom is already of: students. Ask for eight to twelve volunteers (NOT Kevin) to stand up in front of the class and become the medium through which your waves will travel. Tell ‘em they’re “apprentice kineticists” and you’ll likely see more raised hands than you can shake a stick at.
Have your helpers stand shoulder-to-shoulder with each other in a straight line. Make sure that only their shoulders are touching and they’re not bracing themselves against each other in any other way. Once they’re all lined up, stand at one end of the line and gently but firmly push the first students should toward the far end of the line. Repeat as needed, switching ends, with your non-volunteer students making observations all the while.
Now, instruct your helpers to interlock their arms with the student(s) next to them. When that’s all squared up, start pulling and pushing the first student back and forth in a rocking motion until the entire line o’ students is swaying. Again, have the other kids make observations and repeat as necessary.
The first part of this shenanigan of a science experiment demonstrates longitudinal waves (a.k.a. compression waves), which travel parallel to or in the same direction as their medium, whether that medium is water, earth, or smelly human children. The second bit demonstrates transverse waves, which travel perpendicularly to their medium.