Waves lab report

Waves in various liquids lab

How will the different liquids affect the wavelength and the frequency of the wave?

My hypothesis for this lab is that the frequency will be slower, and the wavelength longer in the liquids that are more dense (honey, for example). I think this, because, in more dense liquids, the waves will need much more energy in order to travel through the packed liquid with a high frequency. However, I cannot give the waves the energy (cannot cause a stronger disturbance) they need in order to travel in high frequency, because I have to keep the experiment fair. I think that the waves will travel much more freely and the frequency will be much higher (wavelength shorter), in liquids with lower density (water).  

In order to conduct this experiment there are different materials I used. They are:

• A tray.
• A plasticine stick to cause the disturbance, and create the waves.
• A ruler, possibly plastic, to measure the wavelength.
• A stopwatch, to help you measure the frequency.

The different mediums to test the waves in:

• Water
• Oil
• Honey
• Yogurt
• Orange juice

There are several steps that I took in order to conduct this experiment. The list of steps is below:

• Pour a few cups of water into the tray.
• Then, cause a disturbance by using a plasticine stick (make sure that you keep the force the same; touch the water with plasticine each second)
• With a ruler, measure the wavelength, and, then, using a stopwatch, measure the frequency of the wave.
• Record the speed, and your observations.
• Repeat these steps each time you use another liquid.

My observations

Water- The waves in this liquid moved more freely, and the water has a low density. The waves spread their energy more easily in the water. The wavelength is 2cm, and the frequency is 1 Hertz.
Oil- The oil has a very high density, but not as high as honey, for example. That is why I have noticed that the waves do move, but they do not reach the end of the tray. In order for them to be able to do that, I would need to apply a higher force, but I can’t change that variable, because I need to keep the experiment fair. This wave travels 7cm, and the frequency is 1 Hertz.
Honey- Honey is a very packed liquid, with a very high density. That is why no waves were produced in honey. The waves didn’t have enough energy to pass through such a dense liquid.
Yogurt-  Like honey, yogurt is a very dense liquid, almost in a solid, jelly-like state. No waves passed through, and that is something I expected from such a dense liquid.
Orange juice- I found that orange juice has a density that is lower then oil, but higher then water. The waves did reach the end of the tray, and the wavelength of the wave was 3cm, while the frequency was 1 Hertz.
Another observation I made was that every liquid that actually had a low enough density to produce waves had the same frequency of the waves. So, water, oil and orange juice have, obviously, different densities, and despite that, the frequency of the waves was the same. I think this was because of the force I applied (one small disturbance, per second). I predicted that, if I used a bigger force, creating a greater disturbance, the frequencies could have been different.


I think that my data and my analysis was quite precise, because I repeated the steps for each liquid several times in order to make sure that it is correct. As I said in my hypothesis, the pattern is that the higher the density, the longer the wavelength is, and, therefore, the slower the speed of the wave is.

My conclusion

My guiding question is How will the different liquids affect the wavelength and the frequency of the wave?. And, at the end of this lab, my answer is that the wavelength depends on the density of the liquid, while the frequency mostly depends on the force that is applied to the liquid, less to the density. The variable that I had to keep the same was the force, and the changing variable were the different liquids. I think that my hypothesis was partly correct, but partly not. Only wavelength depends on the liquid’s density, the frequency has nothing to do with the density, just the force applied.

Further inquiry

I think that this lab is very hard, and that it was quite difficult to be precise, and, therefore, there were quite a few areas for error. Firstly, waves move fast, which means that it is very hard to exactly measure the wavelength. Also, it was very hard to use EXACTLY the same force on all the liquids; that is, cause the equal disturbance. By doing this lab, I have developed a few questions, that I would like to find an answer for during the rest of this unit:
1. How does density affect the speed/wavelength of waves? What molecules, atoms, etc. are involved?
2. Is it possible for really packed liquids to create waves? If so, how?