Chapter 3 - Polarization and Spectral Lines

By Johny Jagannath 

Using Goethe's Theory of Color, we have seen that colors in a spectrum are produced by the material; specifically its molecular geometry. This is the basic mesh-analogy that we discussed in my previous post, titled Goethe's Theory of Color. To test this idea, let us view the video shown below. 

This video demonstrates, that green light does not pass through a red filter, but red light passes through a red filter. Similarly, green light does not pass through a red filter, but red light passes through a red filter. This is a behavior that is closely tied to the topic of interest in this post: Polarization and Spectral Lines

[Please view the video, it's a nice one]. 

Below is a diagram that illustrates blue light (per Goethe's Theory) entering a blue filter. 

Therefore once we understand color as a molecular finger print of the material that is emitting it, we can see why a red object looks red and not blue for example. A red object will always look red, unless its molecular geometry is altered. Therefore we are beginning to see a pattern and this can be applied to the prism and the colors that are produced in a spectrum.

We can say, that the prism is simply a device that at certain angles, simulates different types of molecular geometry that are suitable for the production of color.

Therefore, it is clear that when blue light enters a prism, it is able to enter only in locations where the molecular geometry of the prism is suitable for its entry. In all the other locations, it will simply get blocked and the result of this is a single blue line that manged to enter. This is known as a Spectral Line

Therefore each color produces its own characteristic spectral line. To generate yellow light, for example, one needs a sodium lamp. Therefore, observing and documenting how various lamps (with various compounds for varying colors) produce various spectral lines, gives us a benchmark to compare star light for example, to determine various compounds in it, using the spectral lines from star light. This is how one can determine the chemical composition of distant objects. 

With that we've covered the core of spectral lines and their practical uses. We can now move onto Polarization, which is essentially what we observe we when we wear sun glasses to prevent excessive light from reaching our eyes. 

This dimming down of light is essentially polarization. The reader by  now understands why sun glasses are able to dim down light. The sun glasses work like a color filter, whose molecular geometry provides a layer of several meshes that will block portions of light altering the proportions of light and dark reaching your eyes. This will not only dim the light, but also cause a change in color depending on the filter that is in use. And that's polarization.

Next we will look at Doppler effect.


Popular Posts