NUMERICAL-APERTURE TABLE.* 



The " Aprrturk " of an optical Instrument indicates Its arreater or less capacity 

 for receiving rays from tlie object and transmitting them to the Jraage, and tlie 

 apei-ture of a microscope objective Is therefore determined by the ratio oetween its 

 focal length and the diameter of the emei-gent pencil at the plane of Its emergence 

 —that is, the utilized diameter of a single-lens objective or of tlie t>ack lens of a 

 compound objective. 



Tills ratio is exprensed for all media, in all cases by n sin. m, » beingi the refrac- 

 tive index of the medium, and u the senii-angle of aperture. The value of n sin. a 

 for any particular case is the numerical aperture of the objective. 



Theoretical 

 Resolving 

 Power in 



Lines to an 

 Inch. 



= line E.) 



146,528 



144,600 



142,672 



140,744 



138,816 



136,888 



134,960 



133,032 



131,104 



129,176 



128,212 



127,248 



125,320 



123,392 



121,464 



119,536 



117,608 



115,680 



113,752 



111,824 



109,896 



107,968 



106,040 



104,112 



102,184 



100,256 



98,328 



96,400 



94,472 



92,544 



90,616 



88,688 



86,760 



84,832 



82,904 



80,976 



79,048 



77,120 



75,192 



73,264 



71,336 



69,408 



67,480 



65,552 



63,624 



61,696 



59,768 



57,840 



55,912 



53,984 



52,056 



50,128 



48,200 



Penetrat- 

 ing 

 Power. 



•658 



-667 



•676 



•685 



-694 



•704 



714 



•725 



•735 



•746 



•753 



•758 



-769 



-781 



-794 



-806 



-820 



•833 



■847 



•862 



•877 



•893 



•909 



-926 



-943 



-962 



-980 



1-000 



1-020 



1-042 



1064 



1-087 



1-111 



1.136 



1-163 



1-190 



1-220 



1-250 



1-282 



1-316 



1-351 



1389 



1-429 



1-471 



1-515 



1562 



1-613 



1-667 



1-724 



1-786 



1-852 



1-923 



2-000 



MICROMETRIC TABLE. 



L W = one thousandth of a 

 millimetre. 



ins. 

 lOOOO 



"STiffir 



"S55tr 



1 



' Jff 0" 



1 



¥6(» 

 Y(V(J 



Tit) 

 1 



TOu 



1 



1 



'Suit 



1 

 1 



•fOo 



1 

 1 



TOO 

 1 



-is- 

 1 



"?0" 



1 



1 



1 



"TO" 



1 



1 

 S^ 



s 



"To" 



1 

 "T«' 



Example. — The apertures of four objectives, two of which are 

 dry, one water-immersion, and one oil-immersion, would be 

 compared on the angular aperture view as follows : 



106" (air), 157° (air), 142° (water), 130" (oil). 

 Their actual aper- 

 tures are , how- 

 ever, as -80 -98 1-26 1-38 

 or as their numerical apertures. 



• From Journal of the Royal Microscopical Society. 



"Tff" 

 1 



