The Microscope. Its History, Construction, and Application 15th ed. / Being a familiar introduction to the use of the instrument, and the study of microscopical science

by Jabez Hogg

180° Oil Angle. (Numerical Aperture 1·52.)

180° Water Angle. (Numerical Aperture 1·33.)

180° Air Angle. 96° Water Angle. 82° Oil Angle. (Numerical Aperture 1·00.)

97° Air Angle. (Numerical Aperture ·75.)

60° Air Angle. (Numerical Aperture ·50.)

Fig. 35.—Relative diameters of the (utilized) back lenses of various dry and immersion objectives of the same power (¼-in.) from an air angle of 60° to an oil angle of 180°.