Word Finder - prism

definition

A polyhedron with parallel ends of the same size and shape, the other faces being parallelogram-shaped sides.

definition

A transparent block in the shape of a prism (typically with triangular ends), used to split or reflect light.

definition

A crystal in which the faces are parallel to the vertical axis.

If a suitable prism is placed in front of the eyes the double vision may be prevented.

Ladenburg's prism formula would give two enantiomorphic ortho-di-substitution derivatives; while forms in which the hydrogen atoms are placed at the corners of a regular octahedron would yield enantiomorphic tri-substitution derivatives.

By projecting Ladenburg's prism on a plane and numbering the atoms so as to correspond with Kekule's form, viz.

When the pupil of the eye is held half over the edge of the prism a, one sees the image of the object with one half of the pupil and the paper with the other half.

The prism p is fitted accurately into brass slides (care has to be taken in the construction to place the prism so that an object in the centre of the field will so remain when the eye-piece is rotated in its adapter).

The prism and eye-piece are then rotated together in the adapter.

In either case (as also with a prism) the position of minimum deviation leaves the width of the beam unaltered, i.e.

A glass prism of total reflection is sometimes substituted for the plane mirror.

The combination so formed is known as Rochon's prism.

Usually they are interpenetration twins with the principal axis as twin-axis; the prism planes of the two individuals coincide, and the faces r and z also fall into the same plane.

A crystal becomes positively and negatively electrified in alternate prism edges when its temperature changes.

A beam of sunlight admitted into a darkened room through a narrow aperture, and there dispersed into a vario-tinted band by the interposition of a prism, is not absolutely W continuous.

The materials for it were rapidly accumulated by the use of an objective prism, that is, of a prism placed in front of, instead of behind the object-lens, by which means the spectra of all the stars in the field, to the number often of many score, imprinted themselves simultaneously on the sensitive plate.

Thus constructed, the ' prism produces no lateral shift of the transmitted pencil; a conical pencil, incident directly, has nearly constant polarization over its extent, and consequently the error in determining the polarization of a parallel pencil, incident not quite normally, is a minimum.

Sang and sometimes called a Bertrand's prism, it is the ordinary stream that is utilized.

He employed a Nachet combination of prisms and placed the dividing prism at the spot where a special reversing system formed a real image of the exit pupil of the objective.

H Describe how white light can be dispersed by a triangular prism.

These are almost without exception of the roof prism design.

By slightly turning the prism P, the position of the spectrum on the first screen could be shifted sufficiently to cause light of any desired colour to pass through.

The image of this seen through the glass prism of the spectroscope will appear as in fig.

When hardened in situ its shape is that of a right-angled, triangular prism showing five surfaces - superior, anterior, inferior, posterior and right lateral which represents the base of the prism.

The Helena crystals are of tabular habit, being composed of the basal pinacoid with a very short hexagonal prism, whilst at Yogo Gulch many of the crystals affect a rhombohedral habit.

The parallelism, which is required to avoid aberrations, otherwise introduced by the prism or grating, may often be omitted in instruments of small power.

A prism or a train of prisms. These are employed in instruments of small power, especially when luminosity is a consideration; but their advantage in this respect is to a great extent lost, when, in order to secure increased resolving power, the size of the prisms, or their number, is unduly increased.

In the case of a prism some caution is necessary unless the standards used are very close together.

If 1 2 and t l are thicknesses traversed by the extreme rays, t = t 2 - t,, and if, as is usually the case, the prism is filled right up to its refraction cap, = o, and t becomes equal to the greatest thickness of the medium which is made use of.

If a short length of platinum wire be inserted vertically into a lighted Bunsen burner the luminous line may be used as a slit and viewed directly through a prism.

Angular prism spectroscopes are the commonest.

Such an instrument consists of a triangular prism set with its refracting edge vertical on a rigid platform attached to a massive stand.

The prism may be made of a dense flint glass or of quartz if the ultra-violet is to be explored, or it may be hollow and filled with carbon bisulphide, a-bromnaphthalene or other suitable liquid.

Liquid prisms, however, suffer from the fact that any change of temperature involves a change in the refractive index of the prism.

The collimator has a vertical slit at its outer end, the width of which may be regulated by a micrometer screw; in some instruments one half of the slit is covered by a small total reflection prism which permits the examination of two spectra simultaneously.

The scale telescope contains a graduated scale which is illuminated by a small burner; the scale is viewed by reflection from the prism face opposite the first refracting face.

In Browning's form the setting is automatic. The dispersion may be further increased by causing the rays to pass more than once through the prism or prisms. Thus, by means of a system of reflecting prisms, Hilger passed the dispersed rays six times through one prism, and, by similar means, Browning passed the rays first through the upper part of a train and then back through the lower part.

Rutherfurd devised one made of flint glass with two crown glass compensating prisms; whilst Thallon employed a hollow prism containing carbon bisulphide also compensated by flint glass prisms. In direct vision spectroscopes the refracting prisms and slit are in the observing telescope.

The usual form of ice-crystals in clouds is a right hexagonal prism, which may be elongated as a needle or foreshortened like a thin plate.

The parhelia (p) were explained by Mariotte as due to refraction through a pair of alternate faces of a vertical prism.

When in use, the prism is supported some inches above the body and is the only part that can be seen by the enemy.

When the periscope is not in use, the prism is lowered and protects the upper lens in the body.

A neat rainguard made of sheet metal, to the same curve as the body of the periscope and almost 8 inches long, is attached to the upper prism box by two spring straps.

When in use, it is held at right angles to the periscope above the upper window by a bayonet catch; when not in use, it is lowered and sprung round the body of the periscope just below the upper prism box.

Horizontal rays of light entering at the top were reflected by a prism down the tube and focussed on to a sheet of paper in front of the helmsman inside the submarine.

The top is closed by a pressure-tight window, inside of which is a prism which reflects the light rays vertically down the tube to a prism at the bottom end, where they are reflected in a horizontal direction and focussed in an eyepiece attached to the bottom of the tube.

In the skysearching periscope the upper prism can be rotated by mechanism inside the periscope, so that aerial observations can be readily made before the submarine " breaks surface."

It is a curious coincidence, to say the least, that Dieulafoy found among the ruins of the Memnonium at Susa (the ancient Shushan, given as the scene of the events narrated in the Book of Esther) a quadrangular prism bearing different numbers on its four faces.

Soda light, first sifted by passage through a plate of potassium bichromate, traverses in succession a lens, a Nicol's prism, and a glass plate half covered with a half-wave plate of quartz, that is cut parallel to the optic axis and has its principal section inclined at a small angle to that of the prism.

When the plates are of equal thickness, their combined effect is nil, but by adjusting the second, a rotation in the one or the other direction may be introduced, a scale attached to one prism and a vernier to the other giving the thickness of the resultant quartz plate.

In order to correct this, the light after analysation is passed through another plate of quartz and then the sensitive tint may be more or less restored by cutting off some colour, the same for the whole field, by a Nicol's prism placed in the eyepiece of the telescope.

Distinctly developed crystals are, however, of rare occurrence; they are usually acicular with acute pyramid-planes and are repeatedly twinned on the prism.

The edge which is the separating line of the horizontal and hypothenuse surfaces of the prism, lies approximately over the middle of the system, so that the rays entering through the opening in the side after having been reflected by the hypothenuse surface are concentrated through one half of the objective on to the object.