Introduction
This experiment uses chilled vodka in a dish on top of a speaker to show still waves. When certain frequencies are played, waves form in the liquid that appear to be standing still. This is the sound waves creating still waves. In other words, two waves going in opposite directions, combine to create a wave that looks as though it is not moving. So instead of a ripple in the liquid that travels from the center out, or vice versa, we can see waves that, are still in the liquid, give and take a little vibration.
Methodology
For this experiment I started with an old speaker that I had in my garage from an old TV sound system. After finding the right chord, I connected the speaker to my computer and was able to get the speaker to operate. I taped a small circular glass dish to the speaker with masking tape. I then poured vodka that I had chilled in the freezer into the dish. I used chilled vodka because its viscosity works well for the experiment. I was then ready to start testing it out. To test out specific frequencies I used an online tone generator. (https://www.szynalski.com/tone-generator/)
Results
I tested a range of frequencies from 29 Hz to 100 Hz. The clearest standing waves were at 63 Hz and at 72 Hz. 63 Hz required a lower volume than 72 Hz to create the standing wave. This frequency was also able to create two types of standing waves at different volume levels. A lower volume created what can be described as a still ripple and the higher volume level created a pattern that contained many small waves within. The frequencies lower than 63 Hz made the speaker shake too much to create still waves. When I turned the volume down to counter act this, no waves were created in the Vodka. Frequencies higher than 80 Hz created rapid traveling waves with a lot of movement.
This is a video that shows the vodka at frequencies starting at 63 Hz and traveling to 85 Hz.
At 14 seconds we can see the still wave form at 63 Hz. Though the light makes it look as though it is moving, the vodka is barely vibrating in the wave form. At 29 seconds we no longer have a still wave. Again at 50 seconds, a still wave forms and at 1 min 4 seconds the wave has changed. At 1 minute and 6 seconds we see the rapid waves mentioned above.
This is a close up of the still wave at 63 Hz
Discussion
The difficult part of this project was actually the documentation. It was harder to capture a still wave than I had anticipated. I tried different lighting yet every time the reflection of the light in the liquid makes the wave look like it has a ripple effect. The vodka is still vibrating, it is not absolutely still just not moving in a particular direction, and the reflection of the light was moving with the vibration causing a problem when filming. I tried my best to find certain angles that could help show the true wave but I think that it is still a little hard to see in the videos.