QI'ESTfO.XS 271 



62. What arc the disadvantages of too-low or t()o-liiji;li (>yepieccs 

 with any objective? 



53. How can marked curvature of the field i)e axoided? 



54. Why should one consider chiefly the hiji;h-ai)erture ol)jectives in 

 choosing the magnification of the eyepieces? 



55. How can optical errors due to a poor condenser or wrong cover- 

 glass thickness l^e hidden? 



56. How nuich is lost by using the 5 times eyepiece, chiefly or wholly? 



57. What advantage have objectives of lower aperture, when the 

 maximum aperture is not needed? 



58. What are the disadvantages of using a high dry objective of 

 0.85 aperture on work which could be done by an objective of 0.5 

 aperture? 



59. If the work can be done with an oil-immersion objective of 1.0 

 aperture, what disadvantages are there in using an objective of 1.3 

 aperture? 



60. W^hat condenser is best for use with natural or artificial daylight? 



61. When should Corning daylight glass be used? 



62. When is a yellow-green screen of advantage? 



63. What special corrections can be applied: (a) when working with- 

 out a cover-glass; and (6) when working through a cover 0.4 millimeter 

 thick^ 



64. What are the five chief methods of illumination for the compound 

 microscope? 



65. What is the maximum diameter of the source of light to be used 

 with high oil-immersion objectives? 



66. How are source-field, object-field, and image-field defined in this 

 book? 



67. What are the requirements as to size of the source-field for the 

 best vision with the highest powers? 



68. What sources of light may be used for the best vision with the 

 highest powers? 



69. W^hat is the most convenient source of light for both low and high 

 powers? 



70. How can ground glass be arranged to transmit only refracted and 

 diffracted (not direct) light? 



71. What is the use of the diaphragm close to the source of light? 



72. How can the double-ground glass he treated to increase its 

 diffracting power? 



73. If the incandescent horseshoe of a C-Mazda lamp is projected 

 by a large condensing lens, close to it, towards the microscope, and the 

 mirror is put in the concavity of the horseshoe (where it would naturally 

 be when all is centered), how can the microscope be best illuminated? 



74. What is the best way (theoretically) of using the Abbe uncor- 

 rected condenser? 



