I can see from the site visits statistics that many of you have logged in to see whether I’ve posted anything! Sorry if I have been late in putting up something for you to do. We can probably start with building the pocket CD spectroscope.

Before you start, let us recall what spectroscopy means. Remember, a spectroscope splits light into its component colours. Light from different sources made of different materials give different spectral patterns, and studying the patterns can reveal the materials present in the light source.

There are several designs which you can use to make your own spectroscope, but I would recommend this one which I have tried out myself. http://www.amnh.org/resources/rfl/pdf/du_u03_spectroscope.pdf You just need to print out the template on a piece of paper, paste it on a piece of cardboard and follow all the instructions closely. You can also use the design on Arvind Gupta’s toys website- http://www.arvindguptatoys.com/toys/cdspectroscope.html

You can choose either of these designs. Try to read through the instructions and see if you can figure it out yourselves. If you have any questions regarding the construction of the spectroscope, please feel free to post them as comments. I’ll respond to them as soon as I can. All you need is some paper, cardboard, glue and a piece of an old CD!

Once you have made the spectroscope, you can try pointing it at different light sources and study the different spectral patterns that are revealed. Most of you have already seen the spectrum produced by tube light, which closely matches with the spectrum of mercury. You can also try studying the light emitted by CFLs(Compact flourescent lamps- those small white energy-efficient lights), your computer screen, a candle, LED flashlights etc. DO NOT LOOK AT THE SUN DIRECTLY- IT COULD DAMAGE YOUR EYES.

If you are interested in knowing a bit more about spectroscopy you could look at these websites-
http://www.cs.cmu.edu/~zhuxj/astro/html/spectrometer.html
http://www.amateurspectroscopy.com

P.S. The width of the slit which lets light into the spectroscope is crucial. If it is too small, it will not let in enough light and you will not see anything. If it is too wide, it will let in too much light and you will not see a clear, sharp spectrum. Experiment by varying the width of the slit and see if you can find out the optimum width for your spectroscope. Also see if you can modify the design so that you can vary the width as and when you wish!

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