Using the Mini Spectroscope

Here are two spectra I photographed directly from a mini-spectroscope made from a slice of audio CD. The lights used were of the fluorescent tube kind. The first tube is a standard tube and the second one is one advertised as full spectrum, it is brighter and whiter. In both cases the 3 visible signature lines of mercury vapor (Hg) are clearly identifiable (435, 546 and 577,579 of HgI). These lines are marked black on the underlying scale.

Most of the mercury light is actually emitted in the short UV at 253.7 nm (not shown on the scale). The phosphors coating the tube fluoresce under this UV and reemit the light in the visible region. Clearly the full-spectrum lamp makes more generous use of the phosphors: the green and red lines are prominent and a blue line can also be detected. The common phosphor lines are marked by color lines on the scale.

By using a DVD instead of an audio CD the yellow doublet at 577,579 nm can be resolved, but it is not easy to photograph.

Coleman fluorescent camping lantern:
Ott-Lite full spectrum work light:
Mercury (Hg)
Color Wavelength (nm) Ion
Short UV 253.652 Hg I
Long UV 365.015 Hg I
Long UV 404.656 Hg I
Violet 433.922
Hg I
Green 546.074 Hg I
Yellow 576.960
Hg I
IR 708.190
Hg I
Source: Mercury Lines (NIST)
Common Phosphors
Color Peak Wavelength (nm) Phosphor
Blue 450
(Sr,Ba,Ca)10(PO4)6Cl2 : Eu
Green 542
(La,Ce,Tb)PO4: Ce,Tb
(Ce,Tb)MgAl11O19: Ce,Tb
Red 611 Y2O3: Eu
Source Phosphors (Stanford Materials)