(雅思2013年4月6日雅思阅读考题回顾.docxVIP

雅思考试阅读考题回顾朗阁海外考试研究中心 王飞燕考试日期： 2013年4月6日 Reading Passage 1 Title: Radio Question types: Sentence completion填空； Multiple choice单选题 文章内容回顾 讲收音机的制作历史以及制作步骤和流程 英文原文阅读 Radio is the wireless transmission of signals through free space by electromagnetic radiation of a frequency significantly below that of visible light, in the radio frequency range, from about 30 kHz to 300 GHz. These waves are called radio waves. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Information, such as sound, is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude, frequency, phase, or pulse width. When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form. The etymology of radio or radiotelegraphy reveals that it was called wireless telegraphy, which was shortened to wireless in Britain. The prefix radio- in the sense of wireless transmission, was first recorded in the word radioconductor, a description provided by the French physicist édouard Branly in 1897. It is based on the verb to radiate (in Latin radius means spoke of a wheel, beam of light, ray). The word radio also appears in a 1907 article by Lee De Forest. It was adopted by the United States Navy in 1912, to distinguish radio from several other wireless communication technologies, such as the photophone. The term became common by the time of the first commercial broadcasts in the United States in the 1920s. (The noun broadcasting itself came from an agricultural term, meaning scattering seeds widely.) The term was adopted by other languages in Europe and Asia. British Commonwealth countries continued to commonly use the term wireless until the mid-20th century, though the magazine of the BBC in the UK has been called Radio Times ever since it was