Our eyes are capable of seeing only a narrow spectrum of light.
Let AoBo be a plane wave-surface of the light before it falls upon the prisms, AB the corresponding wave-surface for a particular part of the spectrum after the light has passed the prisms, or after it has passed the eye-piece of the observing telescope.
Julius to explain the "flash spectrum" seen during a solar eclipse at the moment at which totality occurs..
The combined effect of the two is to produce a spectrum sloping up from left to right.
He wrote numerous papers on photometry and spectrum analysis in Poggendorff's Annalen and Berichte der k.