PROPER ILLUMINATION 



325 



TABLE VIII-2 



Index of Refraction Relative to Air for Sodium Light 



X = 5893 A 



TABLE VIII-3 



Numerical Aperture (N.A.) and the Related 

 Magnification at 160 mm 



A Comparison of the Angular Aperture Required to 

 Give the Same N.A. of 0.50 



(2a) 



medium 



Dry objective 



Water immersion 



Homogeneous or oil-immersion objective 



