16 



PROGRESS IN MICROSCOPY 



only on longitudinal chromatism (distance between focal points) but 

 also on the numerical aperture nsinu and the magnifying power g of 

 the objective. We think it advisable to show direct the diffraction- 



048a 



Fig. 1.17. Actual aspects of the diffraction pattern. 



pattern structure in white light for three types of objectives: achromatic, 

 fluorite and apochromatic. Computation was carried out taking the 



05- 



04 



>" 



7// 



5^ 6/. 



A 



Fig. 1.18. Gibson and Tyndall curve of the spectral sensitivity of the eye. 



eye as receiver (Gibson and Tyndall curve) and a standard microscope 

 lamp as source whose spectral distribution of energy can be likened 

 to the photometrists' standard A (Fig. 1.19). 



