Bauhaus-Universität Weimar

Titel:
L. E. Knott Apparatus Company: Scientific Instruments, Catalogue 26
Person:
Knott, L. E.
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit13684/129/
124 
L. E. KNOTT APPARATUS COMPANY 
77-350 NEWTON’S RINGS for illustrating colors of thin plates, demonstrating interference of light, etc. 
This apparatus consists of two brass rings between which are locked two glasses, one plane and the 
other convex, of very long focus. The method of locking the two rings is such 
that by means of the screws, the pressure may be regulated. Diameter of glasses, 
1)4 inches. If the two surfaces are exposed to ordinary light in front of the 
window, so as to reflect light, there is seen at the point of contact a black spot, 
surrounded by ü or 7 colored rings, the tints of which become gradually less 
strong. If the glasses are viewed by transmitted light, the center of the ring is 
white and each of the colors is exactly complementary to thàt of the rings by 
reflection. If exposed to light from a monochromatic flame, an interesting study 
of the colored rings presents itself....................................... 
77-375 INTERFERENCE OF LIGHT PLATES (see Millikan & Gale, Fig. 391)..... 
POLARIZATION STUDY APPARATUS 
No. 78-45 No. 78-85 
78-45 PICKERING POLARISCOPE for study of simple objects under polarized light. This is a simple 
form of polariscope in which the polarizing mirror covers the stage. The analyzer is a Nicol’s 
Prism 6-mm. aperture mounted in brass tube. It is provided with pointer and graduated arc. An 
improved holder is provided for specimens to be studied....................................$25.50 
Iceland Spar. Iceland Spar is a crystallized mineral which produces two refracted beams of light from one 
incident ray. Iceland Spar comes in many forms, all of which may be reduced by cleavage to the rhombohedron. 
This mineral comes in many grades of purity and clarity, although the double refraction can be shown by the quality 
readily obtainable, and as generally listed. We recommend our No. 78-75. 
78-75 ICELAND SPAR, best quality, recommended for its remarkable purity and clarity.............. 1.20 
78-76 ICELAND SPAR, large size, medium quality.................................................60 
78-77 ICELAND SPAR, ordinary quality. . . ........................................................35 
Tourmaline Tongs. Tourmaline is a uni-axial negative crystal in the form of a regular hexagonal prism from 
which only the “extraordinary” ray emerges, while the “ordinary” is rapidly absorbed. It can, therefore, be 
used in producing a polarizing light. The optical axis of tourmaline coincides with the prism and for optical purposes 
the plate is cut from it parallel to the axis. In tourmaline tongs used for illustrating and analyzing polarized light, 
two tourmaline crystals are mounted in discs which are held as illustrated. These discs are each free to move. If the 
prisms are placed so that their axes are parallel, light emerges as the prisms are turned so that their axes are at an 
angle. In use, the crystal to be studied under polarized light is placed between the two crystals. 
78-85 TOURMALINE TONGS, simple form, medium size tourmaline prisms, capable of ordinary work. . . 5.00 
NICOL’S PRISMS 
The ray of light incident on the crystal of Iceland Spar is split into two rays, the “ ordinary ” and the 
“ extraordinary,” each of which travels in a different plane. In order that the incident ray may be transmitted 
in one plane it is necessary to dispose of either the “ordinary” or “extraordinary” ray. The Nicol’s Prism 
causes the “ordinary” ray to be totally reflected, allowing the free transmission of the “extraordinary ” ray. 
These types of prisms consist of rhombs of Iceland Spar, each of which is obliquely cross-cut symmetrical to the 
other. Faces polished and then luted by the cement the index of refraction of which is greater than that of the 
“ extraordinary ” ray. This cross cut is of such an angle that total reflection of the “ ordinary ” ray occurs when 
the incident ray strikes the luted faces. Our Nicol’s Prisms are purchased from one manufacturer and are noted for 
their large polarizing field and their exceeding clarity. 
78-95 NICOL’S PRISMS, luted by Canada Balsam, polarizing field of 22)4 degrees. 
a b c 
Aperture................... 6 7 S mm. 
Each...................... $5.75 $7.25 $12.00
        

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