Teaching aids on double refraction and polarized light,

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Deborah Kimberly O’Brien’
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$Teaching aids on double refraction and polarized light, 1820-1920 For at least two decades after R.$ $This included phenomena like double refraction, polarization by reflection, interference effects in polarized light, and optical activity.$ Newton's corpuscular emission hypothesis.

Newton's corpuscular emission hypothesis.

The oldest advertisement which I have found is from the workshop of H. Pixii in Paris, 1824. His catalog offers three different sets of apparatus for this purpose, one of which is described below.

1 Teaching aids on double refraction and polarized light, For at least two decades after R. Malus' 1808 discovery of polarized light, experimental studies on its properties were chiefly the domain of scientists. This included phenomena like double refraction, polarization by reflection, interference effects in polarized light, and optical activity. Teaching on optics in schools and colleges probably continued being limited to geometrical aspects of rays, lenses, simple photometry, spectra and other aspects of light which could be explained by I. Newton's corpuscular emission hypothesis. Gradually however, means were developed by which students and interested members of the public could experience for themselves the remarkable range of visual effects produced by polarized light. The oldest advertisement which I have found is from the workshop of H. Pixii in Paris, His catalog offers three different sets of apparatus for this purpose, one of which is described below. Another early producer of such educational material was J.W. Albert in Frankfurt, who advertised Apparate zu Versuchen über die Polarisation des Lichts in These included specially cut pieces of Doppelspath (Iceland spar), an achromatized double-image prism, and thin plates of doppelspath, aragonite, and quartz With a thin sheet of the dichroic mineral tourmaline on each side of such plates, anyone could observe the different types of multicolored interference patterns discovered by D. Brewster and others around 1820 in transparent respectively uniaxial, biaxial, and optically active crystals. By the early 1830s the undulation theory of Huygens and Young, as modified by A. Fresnel to admit transverse vibrations, had fully replaced Newton's theory in the opinion of scientists. Sections on optics in Physics books had to be rewritten and expanded accordingly. 1

$Moigno, a prolific writer on science, described the situation twenty (and more) years earlier: Il y a vingt ans, les phénomènes de la double réfraction, de la polarisation rectiligne, circulaire,$

2 In 1855 the Abbé F. Moigno, a prolific writer on science, described the situation twenty (and more) years earlier: Il y a vingt ans, les phénomènes de la double réfraction, de la polarisation rectiligne, circulaire, elliptique, mobile ou rotatoire, chromatique, de la diffraction, des interférences étaient regardés comme inaccessibles... Moigno mentions demonstrations of these phenomena which were performed for large audiences in many cities by C. Despretz and others. He claims that they had considerable effect towards reforming this important branch of physics. A major step in the development of teaching aids, was H. Dove's 1835 description of a setup on a two-foot long brass bar for studying polarized light. Dove's drawing of the setup is shown below on the left. It may have been the first optical apparatus where Nicol prisms served both in a polarizing and analyzing capacity. Light coming from the right is condensed by a large lens, passing through the polarizer, other components and the analyzer to the viewer. The inset shows fringes seen in a rapidly cooled plate of glass. Dove's device was very popular for decades; in a report on an exhibition of scientific equipment in 1867 it is called Dove's wohlbekannte Polarisationsapparat. In the right-hand picture, taken from a 1909 textbook, the light comes from the left. An analogous setup with a heater at one end and a thermoelectric sensor at the other, was sold by e.g. N. Lerebours 1853 and E. Ducretet in 1905, both in Paris. It was used for studying properties of heat rays, such as their polarization. A wide selection of objects including polarizers for microscopes, plates of ten different minerals, mirrors, and pieces of strained glass, is presented in a catalog from A. Pritchard in London in A part of his list is shown below. 2

Watkins & Hill in London published in 1838 a list of Apparatus for the Polarisation of Light.

plates, a kit to illustrate transverse wave motion, and the models listed below. A device which was to become even more widespread than that of Dove, was J. Nörrenberg's polariscope.

On the left, light is reflected down by the tilting glass mirror and thereby polarized.

The light is analysed upon reflection from a glass mirror at the top which was often replaced by a Nicol prism as shown in the center picture, or a thin plate of tourmaline as in the right-hand

3 Watkins & Hill in London published in 1838 a list of Apparatus for the Polarisation of Light. Among items offered in this 1½ page advertisement were double-image and Nicol prisms, a dichroscope and a polarizing kaleidoscope, a hollow glass replica of an Iceland spar rhomb, piles of glass plates, a kit to illustrate transverse wave motion, and the models listed below. A device which was to become even more widespread than that of Dove, was J. Nörrenberg's polariscope. It may have been first described in print in 1833, but similar instruments are also attributed to J.T. Mayer and J.B. Biot much earlier. On the left, light is reflected down by the tilting glass mirror and thereby polarized. It is then reflected from a metal mirror in the base up through the glass mirror and through a platform on which transparent objects can placed and rotated. The light is analysed upon reflection from a glass mirror at the top which was often replaced by a Nicol prism as shown in the center picture, or a thin plate of tourmaline as in the right-hand illustration. The latter instrument, designed in 1839 by the optician H. Soleil in Paris, contained lenses and a micrometer. By measuring the size of convergent-light interference figures (as shown above) in biaxial crystal plates, the angle between these axes could be found. These handy polariscopes were sold commercially from 1843 or earlier. With later improvements such as Nicol-prism polarizers, they were featured in many optics textbooks and apparatus catalogs into the 20th century. With simple equipment, one could demonstrate the splitting of an unpolarized light beam into two in Iceland spar. The right-hand diagram shows 3

how the extraordinary beam will move around the ordinary one when a spar rhomb is

A second rhomb of spar, for instance in the holder invented by J.

Huygens' discovery that the character of the light changes on traversing the first

Reflected sunlight was not always available for projecting optical phenomena on to

Artificial illumination by oxyhydrogen flames, coal gas, acetylene, electric arcs,

4 how the extraordinary beam will move around the ordinary one when a spar rhomb is rotated about the direction of the incident light. A second rhomb of spar, for instance in the holder invented by J. Jamin, will replicate C. Huygens' discovery that the character of the light changes on traversing the first rhomb. Reflected sunlight was not always available for projecting optical phenomena on to a large screen. Artificial illumination by oxyhydrogen flames, coal gas, acetylene, electric arcs, and incandescent bulbs kept improving in the 19th century. The setup below is from an exhibition catalog in Projectors were particularly useful for displaying the interference colors in thin sections of minerals and rocks, with the aid of optional polarizing attachments supplied by several makers. From a P. Pellin catalog, Paris 1900: 4

The left-hand instrument below, designed by E.

$study polarized light and double refraction is$ from an E. Leybold Nachf. catalog c. 1908.

along particular directions and polished, were

5 The left-hand instrument below, designed by E. Munier-Chalmas, is in the same Pellin catalog. The right-hand projector with accessories to study polarized light and double refraction is from an E. Leybold Nachf. catalog c Pieces of Iceland spar which had been cut along particular directions and polished, were a popular item in catalogs of educational optics. 5

Paalzow: Among other teaching aids was the Pickering polariscope, in the left-hand illustration.

Simplified versions of polarimeters to observe optical activity in organic liquids such as turpentine and

6 Dove's 1835 rack illustrated on p. 2 gave way in the late 19th century to more sophisticated optical benches, like this one named after A. Paalzow: Among other teaching aids was the Pickering polariscope, in the left-hand illustration. It has a dark-glass polarizer at the base and a small Nicol prism in the eyepiece. Simplified versions of polarimeters to observe optical activity in organic liquids such as turpentine and sugar solutions were also offered. This brief compilation is not exhaustive, but it shows that educational uses absorbed a significant part of the Iceland spar crystals exported in Leó Kristjánsson, Dec

R.B.V.R.R. WOMEN S COLLEGE (AUTONOMOUS) Narayanaguda, Hyderabad.

R.B.V.R.R. WOMEN S COLLEGE (AUTONOMOUS) Narayanaguda, Hyderabad. DEPARTMENT OF PHYSICS QUESTION BANK FOR SEMESTER III PAPER III OPTICS UNIT I: 1. MATRIX METHODS IN PARAXIAL OPTICS 2. ABERATIONS UNIT II