28 



DWYER, NIXON, OVIATT, PEREZ, AND SMAYDA 



INTENSITY OF LIGHT 



LIGHT 

 BEAM 



LIGHT 

 BEAM 



RED 



ORANGE 



YELLOW 



GREEN 



BLUE 



VIOLET 



LIGHT 

 FREOUENCY 

 SPECTRUM 



(a) 



RED 

 YELLOW 



VIOLET 



LIGHT 

 FREQUENCY 

 SPECTRUM 



(b) 



LIGHT 

 INTENSITY 

 SPECTRUM 



INTENSITY OF LIGHT 



LIGHT 

 INTENSITY 

 SPECTRUM 



MAGNITUDE OF VARIANCE 



t POWER SPECTRUM 



OR 

 VARIANCE SPECTRUM 



(0 



Fig. 3 Spectral analysis operating on time-series data is analogous to 

 a prism breaking a beam of light into its colors or wavelengths (from 

 Wastler, 1969). (a) Prismatic resolution of a beam of sunlight, (b) 

 Prismatic resolution of a beam of light, (c) Resolution of a data 

 record by spectral analysis. 



