Prismatic Spectrum Of Sodium


Show the spectrum of sodium, but does not resolve the yellow doublet.◙


Low-pressure sodium source, 10cm focal length cylindrical convex lens, slit, 20cm focal length spherical convex◙lens, and flint glass equilateral prism.◙


Does NOT resolve the yellow doublet.◙

Setup Time

5 min.




The low-pressure sodium lamp produces a line spectrum containing a bright yellow line (the unresolved doublet) as well as several other faint red and green lines. Light from the source passes through a condenser lens and iris and is focused onto a slit by a 10 cm focal length cylindrical convex lens. A 20 cm focal length spherical convex lens focuses the slit onto a distant screen, with the flint glass prism placed in the light just after the spherical lens.