296 



ANGULAR AND NUMERICAL APERTURE 



[Ch. IX 



mersion ; and u, is the sine of half the angle of the light entering the 

 microscope objective, no matter what medium is between the object 

 and objective. 



As there are three factors in this formula, if one knows any two of 

 them the third is readily found: 



469. Table of a Group of Objectives with their Numerical Aperture with Method of 

 Obtaining It. For a Table of Natural sines, see third page of cover. 



Objective 



25 mm. 

 Dry. 



25 mm. 

 Dry. 



i2§ mm. 

 Dry. 



12^ mm. 

 Dry. 



6 mm. 

 Dry. 



6 mm. 

 Dry. 



3 mm. 

 Dry. 



3 mm. 

 Dry. 



2 mm. 



Water 



Immersion 



2 mm. 



Homogeneous 

 Immersion 



2 mm. 



Homogeneous 

 Immersion 



w>55 « 



20" 



40° 



42° 

 IOO° 



75° 

 136° 

 ii5° 

 163 



Q6°I2' 



iio° 3 8 



i 34 °io' 



Natural Sine 



of half the angular 



aperture 



(sin u). 



bin — = 0.1736 

 2 



o. 40° 



bin — = 0.3420 



2 



c- 42° . 



Sin — = 0.3584 



C- IO °° AA 



Sin = 0.7660 



2 



75° 

 Sin i£- = 0.6087 

 2 



Sin = 0.9272 



2 



115° 



Sin — — = 0.8434 

 2 



163 

 Sin ■ = 0.9890 



Sin = 0.7443 



_. no°38' 



Sin ^— = 0.8223 



_. i3 4 °io' 

 Sin-^ 3 = 0.921 1 



Index of 

 Refraction 

 of the medi- 

 um in front 

 of the objec- 

 tive (n) 



n = 1 



11 = 1 



n = 1 



n = 1 



n = 1 



n = 1 



n = 1 



n = 1 



»= i-33 



«= 1.52 



n = 1.52 



Numerical Aperture 

 (N. A.) = n sin u 



N.A. = ix 0.1736 = 0.173 



N.A. = ix 0.3420=0.342 



N.A. = 1 x 0.3583 = 0.358 



N.A. = ix 0.7660 = 0.766 



N.A. = 1 x 0.6087 = 0.609 



N.A. = ix 0.9272 = 0.927 



N.A. = 1 x 0.8434 = 0.843 



N.A. = 1 x 0.9890 = 0.989 



N.A. = 1.33 X 0.7443 = °-99 

 N.A. = 1.52 x 0.8223 = 1.25 

 N.A. = 1.52 x 0.9210 = 1.40 





