PROJECTION MICROSCOPE 



\_CH.IXa 



425. Actual Size of Objects for Demonstration. In the 

 table below are given the objectives and size of objects which can be 

 demonstrated with the apparatus shown in Fig. 204. By inspecting 

 the table one can determine quickly the size of a specimen it is pos- 

 sible to show as a whole, and also the objective to employ. 



The principles involved in the construction of this table are those 

 given in 50, 155. For the low powers a micrometer with coarse 

 lines is necessary. The diameter of the screen image can be meas- 

 ured off directly, with a tape measure or a measuring rod. It is of 

 course the product of the size of the actual field and the magnification. 



TABLE SHOWING THE OBJECTIVES, OCULARS, ACTUAL SIZE 



OF THE FIELD, MAGNIFICATION AND DIAMETER OF 



THE FIELD ON THE SCREEN WITH THE 



APPARATUS IN FIG. 204. 



Distance of the microscope from the screen, 8 meters (26 -f feet}. Arc lamp 

 for illumination. Constant electric current of no volts at the dynamo : 12 amperes 

 going through the lamp. 



