Laser Refraction through Various Liquids

Xiaoxue Jiang

I’d wanted to do a project on lasers all along, given the few (if any) chances I’d get to do so after college. I was always fascinated by their technology and wanted to know how such an advanced, isolated manifestation of science would interact with certain elements of our world. I came up with testing laser refraction through liquids of varying colors and densities, as they would give me a good variety of samples in a consistent form.

Shown below is the basic set-up I used for the experiment. I used a power-meter set to milli-Watt units to measure the power output of the helium neon laser after its refraction through a liquid. This particularly striking substance creating the fluorescent effect is nothing but orange juice.

With this set-up, I collected the following data, making sure to include both distilled water and an empty vial as the control.

Refracting Material Power (mW)
None 3.734
Empty vial 2.885
Water 4.418
Green tea 2.133
Orange juice 0.002
Red water 4
Yellow water 3.375
Green water 0.012
Blue water 0.013

While the results were not as consistent as I’d hoped, I did find a few patterns in the data. Given that the color of the laser was red, I was not surprised by the incredibly low power levels of the laser refracted through green and blue, as it was most likely absorbed rather than reflected onto the power meter. Red water, in contrast, resulted in a high power reading thanks to the same scientific concept.

Orange juice was a different matter entirely, given its high opacity. Rose, who assisted me in the experiment, told me that the opacity scattered the laser light and therefore allowed very little through to the power meter, making its color largely irrelevant.

I’m also unsure as to why water yielded a higher reading than having simply nothing there to refract. With what I have, I can only attribute this to human error. By and large, the results were as predicted given what I knew about electromagnetic waves in the visible spectrum and the principles of absorption/reflection in color.

If I could redo this project, or have an additional six weeks, I would have definitely done multiple trials to ensure the accuracy of my data. There is a possibility that the curtains were not fully drawn to prevent outside light from affecting the reading. I would have also used more materials, perhaps even solid ones such as quartz or crystal if I could acquire it in time.

I am generally happy with the opportunity I was presented with to work with lasers in a safe and controlled environment. I enjoyed learning more about them (specifically the scattering phenomenon in an opaque liquid) and getting some hands-on experience in the scientific method.

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