# Using geogebra for optics

New subject for this post. Since my new position at the crm2 in Nancy, I am working with optics.

We set up an experiment on interferences and optical diffraction for demonstration. I am looking for a free open source software to sketch them. Nothing dedicating to optics exists so I must use something else. I have seen two options so far: a drawing software like inkscape or a geometry software like geogebra.

I tried geogebra for the diffraction of an optical disc. The main disavantage is taht there is no easy access to proportionality like in a refraction and must use equivalent geometry construction.

For example, the refraction law is : $$n_1 \sin(\theta_1) = n_2 \sin(\theta_2)$$

To draw it you need to use cirles to get access to the sine of the angle. It complicates the drawing a bit.

For teaching purpose, geogebra can be really nice because of its interactive drawing. You can introduce variables and allow points to be moved. It is also possible to export the drawing as a java applet to publish it on the Internet. I have done it for optical diffraction through a polycarbonate medium (i.e. a CD or DVD). Click on the picture below to open the applet.

For an optical set up, it is difficult to see if it is efficient, there should not be too much of the problem above, most of the times, only reflections and transmissions are used. But the laser has a certain width and I don’t know if there is any easy way to handle focusing elements.

For a conclusion, I would say that geogebra or a similar software is worth to have a look for optics. It may not be useable for every situation but it can have some use.

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