这有不少，题目吗，随意出点即可，高中生好对付。 Telescope LIGHT and other kinds of electromagnetic (电磁) radiation coming from the universe outside the earth must travel enormous distances through space and time to reach Only the brightest and nearest stars can be seen with the unaided To see farther， a telescope is The word telescope is derived from the Greek words tele， "from afar"， and skopos， "viewer" Even a simple homemade telescope can clearly show Saturn's (土星) rings， Jupiter's (木星) bands and red spot (大红斑)， stars， nebulae (星云)， and nearby The ability to study the distant planets and other structures in the universe with these powerful yet remarkably simple instruments has revolutionized mankind's understanding of the natural All telescopes gather radiation from distant objects over a large area and focus it， thereby increasing the intensity of the radiation and allowing the objects to be magnified (放大) Sophisticated telescopes are used to view radiation in all parts of the electromagnetic spectrum (电磁波谱) from long-wave radiation to infrared (红外线) radiation and light and much shorter wave radiation， including ultraviolet (紫外线) and X This radiation travels through space at the speed of light in the form of waves of electric and magnetic Because of its basic similarity， all such radiation can be focused by reflecting it off a curved surface or by refracting， or bending， it with glass lenses (镜头) The devices that are used to do this， however， vary， depending on the wavelength or type of radiation being Optical telescope The first telescope developed， and the one most widely used， is the optical The light-gathering power of a telescope is determined by the diameter of its objective mirror or This light-gathering power determines how faint an object the telescope can Reflecting telescope A typical reflecting telescope used by an amateur astronomer may have a primary mirror measuring 10 to 20 cm in Reflecting telescopes used by professional astronomers usually have mirrors that measure more than 152 cm in One of the largest is a 600 cm telescope in the Caucasus Mountains of Eastern Europe that began operating in (Part I)(SD-Agencies) Websites African studies Target age range: 6-12 : 13-17 Kids resource page about the people and cultures of A This page chronicles (记述) the daily lives of African communities， with reference materials about geography， cultural exchanges， and educational _Studies/AShtml Target age range: 13-17 : 18 and over Internet resources about the continent of A This site has numerous links to educational resources about African culture and history for all _Studies/Country_Specific/Ahtml Target age range: 13-17 : 18 and over Internet directory of resources about A This site has information about the people and culture of this nation， and links to other Internet sites， as well as basic geographical， government， and history (Part I)(SD-Agencies)
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