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Light Measurement Handbook © 1998 by Alex Ryer, International Light Inc.

9 Graphing Data

Line Sources

Discharge sources emit large amounts of irradiance at particular atomic

spectral lines, in addition to a constant, thermal based continuum. The most

accurate way to portray both of these aspects on the same graph is with a dual

axis plot, shown in figure 9.1. The spectral lines are graphed on an irradiance

axis (W/cm2

) and the continuum is graphed on a band irradiance (W/cm2

/nm)

axis. The spectral lines ride on top of the continuum.

1.10

2.81

1.46

0.32

Another useful way to graph mixed sources is to plot spectral lines as a

rectangle the width of the monochromator bandwidth. (see fig. 5.5) This

provides a good visual indication of the relative amount of power contributed

by the spectral lines in relation to the continuum, with the power being

bandwidth times magnitude.