A wire magnetized longitudinally and circularly becomes twisted.
Maas in Results of In its arrangement the muscular tissue the "Albatross " Expedition, forms two s stems: the one composed Museum of Comparative Y P Zoology, Cambridge, Masse, of striated fibres arranged circularly, that U.S.A. is to say, concentrically round the central FIG.
A wire or rod in this condition is said to be circularly magnetized; it may be regarded as consisting of an indefinite number of elementary ring-magnets, having their axes coincident with the axis of the wire and their planes at right angles to it.
If the wire consists of a ferromagnetic metal, it will become " circularly magnetized by the field, the lines of magnetization being, like the lines of force, concentric circles.
Maxwell has also given an explanation of the converse effect, namely, the production of longitudinal magnetization by twisting a wire when circularly magnetized by a current passing through it.
Twisting a circularly magnetized wire produces longitudinal magnetization.
Their ectodermal muscles are mainly longitudinal, their endodermal muscles are circularly arranged on the body-wall.
The muscular system of the Scyphomedusae is developed on the subumbral surface as a system of circularly disposed fibres which by their contraction make the umbrella more concave and diminish its FIG.
In its optical characters, quartz is also of interest, since it is one of the two minerals (cinnabar being the other) which are circularly polarizing.
Circularly polarized light he obtained by means of a rhomb of glass, known as "Fresnel's rhomb," having obtuse angles of 126°, and acute angles of 54°.
By means of circularly disposed muscular fibrils formed from the endoderm the tentacles can be protracted or thrust out after contraction.
He then points out why " the object-glass of any Telescope cannot collect all the rays which come from one point of an object, so as to make them convene at its focus in less room than in a circular space, whose diameter is the 50th part of the Diameter of its: Aperture: which is an irregularity some hundreds of times greater, than a circularly figured Lens, of so small a section as the Object-glasses of long Telescopes are, would cause by the unfitness of its figure, were Light uniform."
If this axis be parallel or perpendicular to the primitive plane of polarization, the emergent beam remains plane polarized; it is circularly polarized if the axis be at 45° to the plane of polarization, and in other cases it is elliptically polarized with the axes of the elliptic path parallel and perpendicular to the axis of the plate.
Conversely a quarter-wave plate may be employed for reducing a circularly or elliptically polarized stream to a state of plane polarization.
They may, however, be distinguished by the fact that on previous transmission through a quarter-wave plate this property is retained in the case of common light, while with the two other types the relative intensity of the streams depends upon the orientation of the rhomb, and with circularly polarized light one stream may be made to vanish.
The phenomenon of interference produced by crystalline plates is considerably modified if the light be circularly or elliptically polarized or analysed by the interposition of a quarter-wave between the crystal and the polarizer or analyser.
But the most important case, on account of its practical application to determining the sign of a crystal, is that in which the light is plane polarized and circularly analysed or the reverse.
Let us suppose that the light is circularly analysed and that the primitive and final planes of polarization are at right angles.
Fresnel showed that rotary polarization could be explained kinematically by supposing that a plane-polarized stream is resolved on entering an active medium into two oppositely circularly polarized streams propagated with different speeds, the rotation being rightor left-handed according as the rightor left-handed stream travels at the greater rate: The polarization-vector of the primitive - stream being = a cos nt, the first circularly polarized stream after traversing a distance z in the medium may be represented by = a cos (nt - k i z), ni = a sin (nt - kiz), and the second b z = a cos (nt - k 2 z), n2= - a sin (nt - k2z).
Since the two circular streams have different speeds, Fresnel argued that it would be possible to separate them by oblique refraction, and though the divergence is small, since the difference of their refractive indices in the case of quartz is only about o 00007, he succeeded by a suitable arrangement of alternately rightand left-handed prisms of quartz in resolving a plane-polarized stream into two distinct circularly polarized streams. A similar arrangement was used by Ernst v.
According to Fresnel's explanation the light in each of the interfering streams consists of two trains of waves that are circularly polarized in opposite direction and have a relative retardation of phase, introduced by the passage through the quartz: the central fringes are then due to the similarly polarized waves; the lateral systems are produced by the oppositely polarized streams, these on analysation being capable of interfering.
Common light, circularly polarized and partially circularly polarized light all have the characteristic of giving two streams of equal intensity on passing through a rhomb of Iceland spar, however it may be turned.
When the light is circularly polarized or circularly analysed, a single plate gives two mutually enwrapping spirals, and similar spirals in circularly polarized light are obtained with plates of an active biaxal crystal perpendicular to one of the optic axes.
Thus if A = 42, p. must exceed 7r/8 or 2.414, that is, the substance must be at least as highly refracting as a diamond: if A =7 /4, µ must be greater than 37r/16 or 1.4966, and when this is the case, it is possible by two reflections to convert into a circularly polarized stream a beam of light polarized at 45° to the plane of incidence.
This is the principle of Fresnel's rhomb, that is sometimes employed instead of a quarter-wave plate for obtaining a stream of circularly polarized light.
The shadow of a circular disk and of a screen circularly perforated.