Dancing Salt (Sound and Light)

Activity: For this activity we covered a drinking glass with a piece of plastic wrap and secured it with a rubber band. We then sprinkled salt on top of the plastic. We hit a tuning fork and then held it over, without touching the plastic and watched the salt “dance”.

Scientific Principles:  The scientific principle we were learning about through this activity was sound waves. Sound travels through longitudinal waves that create vibrations. The vibrations is what is causing the salt to move in this experiment. Sound waves can travel through air, water or other objects then vibrate in our ears. Because there is no air in the vacuum of space sound can’t travel there!

Point: The point od this activity is for students to be able to see and hopefully understand how sound waves vibrate through the air and interact with the environment.

Introduction: To introduce this to the class I would start with something they know, water waves. How the shape of a pebble hitting a lake creates ripples in the water and how that is similar with what sound does to the air.

Difficulties: The only difficulty that students may have with this activity is getting to tuning fork close enough to the plastic wrap without actually touching the fork to it.

Extensions: A couple ideas for extensions to this activity would be to put the tuning fork in water so that students can actually see the waves and not just the effects they have. I would also have them use tuning forks of different pitches that create different wavelengths.

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