When Röntgen discovered X-rays in 1895, he immediately searched for a means to focus them 4,5. On the basis of uncertain observations of slight refraction in prisms, he stated that the index of ...
State of the art, one of the seven wonders of the Ancient World, the great lighthouse of Alexandria, built around 280 B.C., towered some 450 feet above Egypt's greatest harbor. At that height, it was ...
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