No. 54 541. 



Interference Bands, Diffraction Phenomena. 



547 



54 540 B (54668). 1 : 6. 



54541. 1:8. 



* 54,540. Large Optical Bench for Interference and Diffraction Experiments, Figs. 54,540 A J 



and 54,525, with auxiliary apparatus and box for same; for use with the Heliostat or 

 Projection Lantern 



The bench is of iron, 1.20 m long, and is provided with levelling screws. It has a graduation in 

 millimetres. Each of the three sliders has an index, one of these indices having cross motion for accurate 

 adjustment. The screens fitted for taking the various gaps, gratings, apertures, lenses, etc. can be 

 adjusted vertically on the pillars, in addition to being adjustable laterally. The following pertain to 

 the bench: 1 cylindrical lens, 1 interference prism, 1 Fresnel ocular micrometer (Fig. 54,525) for 

 measuring wave length, with red observation glass; 1 double adjustable rotary micrometer gap, Fig. C; 

 1 rotary gap with screw adjustment, 1 rotary double grating on glass, 3 screens for taking 12 diaphragms 

 having apertures of different shape and with gratings and gaps of different width. The set of dia- 

 phragms consists of: 1 diaphragm with sharp edge, Fig. D; 1 diaphragm with thick needle. Fig. E; 

 1 slot diaphragm with a hair, Fig. F; 1 diaphragm with a thick opaque fibre, Fig. G; 1 diaphragm 

 with a small round aperture for Grimaldi's experiment, Fig. H; 1 diaphragm with large round aperture; 

 1 diaphragm with aperture half covered over with mica, Fig. J; 1 diaphragm with rhombic aperture. 

 1 diaphragm with triangle of holes, 1 diaphragm with two holes, 1 diaphragm with network of holes, 

 and 1 diaphragm with a row of holes. 



* 54,541 . Diaphragmic Disc with 9 Schwerd apertures for diffraction phenomena, Figure, 



rotary, on Stand, for use with sunlight or electric light 



* Can be used with the Projection Apparatus. 



Cl. 309, 327, 

 310 



s. d. 



27.0.0 



1.10.0 



35* 



