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Gherkin Physics

January 22, 2011
First of all – please do not try this at home. It’s VERY DANGEROUS.

If you saw me speak at “Nine Lessons” this year, then you will have seen me electrocute a gherkin containing sodium chloride to show that sodium atoms emit yellow light, with a wavelength of 594nm. Sometimes people ask me if the light is definitely linked to the sodium atoms, or is it the sort of light one might expect from a sooty flame or any hot object? I then raised the question among some physicists.

Dr. Michael de Podesta at the National Physical Laboratory decided to investigate. Here is his email to me.

Some time ago you gave a talk to some Science Ambassadors in the course of which you showed the yellow light that emanated from a ‘gherkinator’. I remember asking you if it really was from the sodium or just a yellow hot-carbon flame?

Anyway, I just thought I would let you know that, as you stated, it is indeed from the sodium and I attach a couple of  photographs showing my own gherkinator and hand held spectrometer, and a (rather poor) photograph of the view down the spectrometer. The yellow line comes out pretty close to 589 nm. Enjoy!

All the best

Michael

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