CASSEGRAIN TELESCOPE
A Cassegrain telescope is a wide-angle reflecting telescope with a concave mirror that receives light and focuses an image. A second mirror reflects the light through a gap in the primary mirror, allowing the eyepiece or camera to be mounted at the back end of the tube. The Cassegrain reflecting telescope was developed in 1672 by the French sculptor Sieur Guillaume Cassegrain. A correcting plate (a lens) was added in 1930 by the Estonian astronomer and lens-maker Bernard Schmidt (1879-1935), creating the Schmidt-Cassegrain telescope which minimized the spherical aberration of the Cassegrain telescope |
ARCHIMEDES
Archimedes (287-212 BC) was a prolific ancient Greek mathematician. Archimedes invented the water screw, a device for raising water using an encased screw open at both ends. The screw is set an an angle, and as the screw turns, water fills the air pockets and is transported upwards. The Archimedes screw is still in use today. Among his many accomplishments was the first description of the lever (around 260 BC). Levers are one of the basic tools; they were probably used in prehistoric times. Many of our basic tools use levers, including scissors (two class-1 levers), pliers (two class-1 levers), hammer claws (one class-1 lever), nutcrackers (two class-2 levers), and tongs (two class-3 levers). |
BAROMETER
barometer is a device that measures air (barometric) pressure. It measures the weight of the column of air that extends from the instrument to the top of the atmosphere. There are two types of barometers commonly used today, mercury and aneroid (meaning "fluidless"). Earlier water barometers (also known as "storm glasses") date from the 17th century. The mercury barometer was invented by the Italian physicist Evangelista Torricelli (1608 - 1647), a pupil of Galileo, in 1643. Torricelli inverted a glass tube filled with mercury into another container of mercury; the mercury in the tube "weighs" the air in the atmosphere above the tube. The aneroid barometer (using a spring balance instead of a liquid) was invented by the French scientist Lucien Vidie in 1843. |
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GEIGER COUNTER
The Geiger counter (sometimes called the Geiger-Muller counter) is a device that detects ionizing radioactivity (including gamma rays and X-rays) - it counts the radioactive particle that pass through the device. The German nuclear physicist Hans Wilhelm Geiger (Sept. 30, 1882- Sept. 24, 1945) developed the device from 1908-12. At that time, Geiger was an assistant to the British physicist Ernest Rutherford (1871-1937). [Geiger's work helped Rutherford discover that radioactive elements can transform into other elements and that atoms have a nucleus]. In 1928, the Geiger counter was improved by the German physicist E. Walther Muller.
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