Spectra and Materials
Name: Tiffany and Victoria
When we were refracting light through liquids, we were able to produce a spectrum
using baby oil, however, it was not as vibrant as the two we produced using water and vinegar.
What properties of the oil caused this? We are guessing it is the density of the oil.
Your results depend on the refractive index of the liquid -- the way light rays bend as they
pass from air into and back out of the liquid. Try the experiment with a clear cooking oil.
Also, you might try pouring some of the liquids into a transparent drinking glass and then
leaning a drinking straw in the glass. Look in from the top and through the side of the
glass to see how much the straw "appears" to be bent. What you see is an illustration of the
liquid's refractive index.
The refractive index of water for the sodium D line (the usual optical wavelength used) is about
1.333, for decane it is 1.409 so at first glance one might expect that octane would "bend" the
light more. However, you also have to take into account the index of refraction of the
container, because the light path is air/container/solution/container/air. Water and vinegar
should behave similarly since vinegar is only 5% acetic acid (index of refraction = 1.370).
The index of refraction of the container changes the path length that the light travels. The
larger the differences in index of refraction between the various substances the "more
brilliant" the spectrum should appear. The classic example is air/diamond vs. air/glass.
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Update: June 2012