Illinois Junior Academy of Science - Yearbook (Urbana, IL)

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the plates was decreased with each exposure and the results analyzed. As the number of photons striking the film de- creased, there seemed to be some irregularity in the pat- terns. This conclusion was not decisive because of the dif- ficulty in reading the films and detecting the faint inter- ference patterns. UHF Oscillators I MICHAEL MARENTIC An oscillator is a voltage amplifier with feedback from the plate, output, to the grid, input-. The prefix UHF, ultra high frequency, is the frequency range from 3 x 10' through 3 x 10' cycles per second. In my project I used only single triode tube oscillator circuits, the Hartly and the parallel line oscillator. My hypotheses were that wiring techniques should have a profound effect on the oscillators, as well as different circuits and tubes. The suppositions were sup- ported by my work. Frequency measurement was at first a serious problem. All the methods I used were ways of meas- uring the placement of standing waves in a parallel line transmission line. The method that worked best was to move a shorting bar along the line and notice the dips in voltage as indicated by a meter connected through an amp- lifier to the ends of the transmission line. The highest fre- quency that I was able to obtain was 760 megacycles, a wavelength of 40 centimeters, using an acorn tube in a parallel line circuit. The frequency of the oscillator isn't that great, but granted it is well into the UHF region of the electromagnetic! spectrum. I hope to try some other acorn tubes or lighthouse tubes in the oscillator circuit. I should get the frequency past at least 1,000 megacycles,

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thermodynamics could lead to the use of rockets and jets, but a project such as this would have to be done on a larger and more complicated scale than mine was. Hilsch Vortex Tube ROBERT M. KIECKHEFER ray Countryside School Barrington Sponsor: Mr. Donn P. Branstrator The Hilsch tube demonstrates that air can be used as a refrigerating gas. The tube was invented by G. J. Ranque, in 1932, and improved by Rudolf Hilsch during World War II. The Ultrasonic Corporation was going to cool refrigera- tors with the tube, but went bankrupt before it could. .The tube is presently used for aircraft thermometers. In my experiment, three tubes were built. Lack of pre- cision prevented tube number one from working. Tube number two achieved temperature extremes of 349 F. and 96' F., while tube number three reached -16 F. and 1460 F. Operation results from incoming compressed air that spins around the spiral chamber and is compressed even more by centrifugal force. Some air expands toward the center of the chamber and is drawn through the diaphragm and out the cold tube. This air is cold because it is expanded. The rotating air in the spiral rotates out the hot tube. Be- cause of friction, the air slows down and expands. Some air is drawn back toward the spiral because of the low pressure area found in the center. This air absorbs heat from the air going out the cold tube. Because of centrifugal force, the recirculated air is drawn toward the outside and starts the cycle over again. Because it has absorbed heat, this air makes the hot tube even hotter. Many parts of the electric refrigerator are similar to parts in the Hilsch tube. Applying the Spacetime Continuum KEVIN KILLION Gordon Tech High School My project this year was a continuation of an earlier study on the nature and properties of the spacetime con- tinuum. By using this project as a basis, I attempted to further investigate the properties of the continuum, and to develop applications for the continuum, on a theoretical basis. By defining a single property of the continuum and deter- mining the effects produced by each of these features, I expanded on known and accepted information about these effects to propose applications for them. or methods of alter- ing them. . The project also expanded on these known properties to determine effects arising from alteration of the continuum. Using the continuum theory as an assumption, a reason for the formation of quasi-stellar sources was proposed. It was further proposed that a secondary protational field exists, which may suggest methods of increasing gravitational strength by rotating or accelerating masses. Several theoretical applications in transportation, com- munication, and matter research were found for a number of continuum features. The project concludes that although such application and experimentation is not currently feas- ible, theoretical work in this field will yield substantial in- formation, particularly on the nature of matter and physics in general. 'DONNA KRISTOVICH Washington High School Determining the Index of Refraction and Optical Rota- tion of Certain Solids and Liquids With Plane Polarized Light. Also determining the color effects produced by the interference of the fast and slow rays in anisetropic sub- stances. Materials: Polaroid sheets, pipe fittings, vanity mirror, orange cans, flashlight, light bulbs, detergent bottles, meter sgck, protractor, glass plates, solutions, plastic and cello- p ane. How is the index of refraction determined? Snell's Law. Brewster's Law. The theory of plane polarized light. Reflection - Refraction - Absorption - X What are Isotropic and Anisotropic Substances? Fast and Slow rays. How is the Specific Rotation of solutions found? How are color effects produced by cellophane wedges by polarized light? What are some of the applications of plane polarized light in science and commerce? Interference ot Light Waves as a Probability Function JOHN A. LaFATA Griffin High School Springfield, Illinois An interference pattern results when light is projected through two narrow slits. If light is thought of as waves, the two-slit interference pattern is easily explained and understood --- superposition and cancellation. But, if light is thought of as particles, how is the interference pattern explained? The interference of light as particles Cphotonsl must be based on a probability factor. Since rules of prob- ability only hold up after a large number of events have occurred, if only a few photons are allowed to strike a photo- graphic plate, shouldn't an irregular interference pattern be formed? Several photographic plates were exposed to light pass- ing through two narrow slits. The number of photos striking

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