Practical Physics [antikvár]

Background Measurement of length is of the age of human history. Measurement, in general, means comparison with a fundamental standard. Standards have to be chosen on the basis of criteria such as accuracy,reproducibility, and convenience. So it is obvious that scientists have sought a natural, universal standard, instead of the king's foot which was the primary standard of length in ancient times. Eighteenth-century French scientists proposed the meter (m), a unit of length that they defined as equal to one ten-millionth of the distance from one of the earth's poles to the equator. Till 1960 the meter was defined as the distance between two lines engraved on a Pt-Ir bar. Its reproducibility was -7 about 2*10 m. As science and technology developed, this precision became inadequate. So the meter was redefined in 1960 as the length equal to 1,650,763.73 wavelengths of the A~0.606 p light emitted by krypton - 86 atoms. Its reproducibility is - 9 ~ 10 m. The SI unit of length is the meter. The most common instruments for measuring lengths are the following: -meter stick, measuring tape, spring-rule -slide gauge -micrometer screw -reading microscope -comparator -measuring instruments based on interference of light. Experimental 1. Measure the sizes of the given parallelepiped by slide gauge. Determine its volume.