report 2... - Report of 2nd Experiment Inverse Square Law...

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Report of 2 nd Experiment Inverse Square Law Using Photocell
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Photocell: A photocell is a type of resistor. When light strikes the cell, it allows current to flow more freely. When dark, its resistance increases dramatically. Photocells need some calibration to be responsive in the exact lighting scenario you have. They can be used to detect large or small fluctuations in light levels to distinguish between one light bulb and two, direct sunlight and total darkness, or anything in between. Each scenario requires a slightly different voltage divider setup, which we'll get into below. The Photocell Daylighting Sensor is a low-voltage daylighting sensor that measures changes in ambient light and controls its connected lighting loads according to the user’s programming. The unit is able to decipher minor changes in light levels (such as passing cloud cover, intermittent shadowing, etc.) to prevent unwanted or inadvertent light cycling. The photocell provides a truly effective energy conservation lighting control system by harvesting daylight, reducing your energy costs Optical table : An optical table is a piece of equipment used for optics experiments and engineering . In optical setups, especially those involving interferometry , the alignment of each component must be extremely accurate—precise down to a fraction of a wavelength —usually a few hundred nanometers . Even small vibrations or strain in the table on which the elements are set up might lead to complete failure of an experiment. Hence, one requires an extremely sturdy table which neither vibrates nor flexes, even under heavy loads. The surface of the table must also be quite flat, to allow precision optical mounts to make good contact with the table without rocking. Earlier optical table tops were sometimes made of a large slab of highly polished granite . The heavy, dense material strongly damped vibrations producing a very stable surface for precision optics. Granite (like wood) damps vibrations because it is a composite material. Such tables were very heavy and expensive, however, and are not commonly available today. Density: ► Definition of Density: The mass density or density of a material is defined as its mass per unit volume . The symbol most often used for density is ρ (the Greek letter rho ). In some cases, density is also defined as its weight per unit volume although, this quantity is more properly called specific weight . The reciprocal of the density of a substance is called its specific volume , a representation commonly used
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in thermodynamics . Density is an intensive property in that increasing the amount
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This note was uploaded on 05/11/2011 for the course UBIT 411 taught by Professor Saleemelahi during the Spring '10 term at University of Karachi.

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report 2... - Report of 2nd Experiment Inverse Square Law...

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