The adjustment of spectrometer and measurement of the prism's refrective index is a classic，general

physical experiment. In this experiment，students can directly see the Mercury spectrum

through prisms，which is vivid，while they do not explore the formation mechanism of atom spectrual lines. On the

contrary，the experiment of Sodium spectrum is a classic，modern physical experiment. Students

understand the nature of atoms and spectrual lines through the calculation of quantumn defects and

the drawing of energy level figures. This experiment combines the thoughts of these two experiments，where students first observe spectrual lines with familiar spectrometers，and calculate the s-and p-quantum defects of Sodium with interpolation methods to understand the characteristics of at- oms. The results ( 1.348 and 0.882，respectively) are in line with the ones carefully calculated，proving that this i- dea is rather practical.