Purdy

Nothing very exciting to report today so here is Purdy!

Yesterday's optical instrument was a diffraction spectroscope.  The device splits light into its constituent colours (wavelengths) as it passes though the diffraction slit. Some alternative designs use a prism for the same purpose and are called refraction spectroscopes.  

So what is its use?  It can be used to analyse the constituent colours of light or to confirm that light is of just a single colour of a precise wavelength.  This may be useful for optical experiments or analysis but a more practical use is for experts to confirm if certain gemstones are genuine or synthetic as only the genuine stones will refract the correct wavelength.