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Function To show the birefringence. |
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Description We place the crystal on a paper sheet, on which a large point is drawn. By looking vertically we see two points, and if we turn the crystal on the plane we will see that one of the two points is at rest while the other turns around the first. | |||
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Function To study the light polarisation. |
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Description It is the easiest polarisation apparatus. It is made of two tourmaline plates, that were cut parallelly to the optics axis of the tourmaline crystal. They are fixed in disk-shaped supports which are turning in the handle. A ray that strikes one of the two plates (polariser) is refracted twice; the ordinary ray is absorbed by the plate, while the extraordinary ray appears more or less coloured (green, brown, red) according to the tourmaline. The second plate is used as analyser; when the tourmalines are crossed the field appears dark. When the tourmalines are parallel the field is bright. The polariser and analiser can be exchanged at will: the fact does not change. | |||
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Function To study the fluorescence. |
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Description We have a glass cube in uranium and some smaller cubes in fluorine and didymium glass. If these substances are reached by a beam of U.V light, the layer in front gets very luminous and diffuses a light that gets paler in the deeper layers. Its colour changes with the sample under examination (green, blue, red). If we put two cubes in file, only the first shows the fluorescence. | |||
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Function To study the phosphorescence. |
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Description We have three flat tubes closed and filled with phosphorescent substances that show a different colour. The phosphorescence is brighter and more durable when the substances are excited by a light rich of UV radiation or X rays. | |||
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Function To study the functioning of the microscope. |
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Description A little bench supports some cursors with an elastic fork on a trapezoidal slide guide. They are used as support to the lenses and diaphragms. A legend indicates the position and the distance on which the single parts are placed. The reference is facilitated by the lateral metric scale. It is opportune to use a fine metallic net or a small slide as object. | |||
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Function To study the functioning of the telescope. |
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Description A bench is used as support. The spring forks can receive equally the lenses and diaphragms added to the apparatus, because the 4 cm diameter is the same for all. Directions with an image indicate the position of the single pieces to realize the different combinations (Galilean telescope, long and short; terrestrial and astronomical telescope). | |||
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Function Functioning of Porro’s prismatic telescope. |
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Description The apparatus shows clearly the path of the rays due to the different reflections and shows the way of forcing a big focal distance into a small format. The total internal reflection prisms are substituted by two couples of flat mirrors placed at right angle and with an inclination of 45 degrees considering the horizontal and vertical stretch of the rays. | |||
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Function To study the camera obscura. |
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Description It is made in varnished wood, with a 45-degrees mirror, and a simple brass objective. The back side of the camera can be raised with a hinge. | |||
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Function To project either transparent or opaque objects. |
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Description The model has two different objectives for the projection of objects and for the projection of slides. | |||
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Function To show the functioning of a camera. |
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Description The camera has a shifting bellows, a reflex and a sporting view-finder. Optics Compur. It uses 4 x 6 cm plates. A purse to keep three plates is supplied with it. | |||
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Function Schematic model of the eye. |
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Description A schematic eye is reduced to a small camera obscura with a simple objective with a 8 mm focal and with a sliding polished screen. On the tube that holds the screen, three signals, marked with the letters M, N, P, correspond to the position for which the image of a far object is formed before the screen, (myopic eye), on the screen, (normal eye) and behind the screen (long-sighted eye). For the N position the image is neat, but for the other two positions the image will result neat only when we pull down the converging lens signed with the M letter, or the converging lens signed with the P letter. The measure of the two additional lenses is two dioptres. | |||
