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A. educational B. observe C. reference D. rough E. appearance |
In 1822, a French physicist named Augustin Fresnel invented a lens (透 镜) that would prove to be very important in lighthouse technology. With the invention of the Fresnel lens, it became possible to make a beam of light reach as far as 28 miles from shore!
Lighthouse beam can be used to help sailors identify the lighthouse and their own location. Sailors canthe patterns and lengths of lights from the lighthouse. Then they look it up in abook that will tell them which lighthouse they have seen.
During the day, sailors can identify lighthouses simply by their. Some are short and fat, while others are tall and thin. They can be made of many different materials, such as wood, stone, brick and steel. The patterns also differ greatly. Some lighthouses are painted with stripes or a series of diamond shapes that make them look different. Others can be recognized by their shape-round, square or rectangular.
Many lighthouses are not in use. They are sometimes changed into museums, inns,centers, or even private homes. If you ever have a chance to visit one, getting glimpse of history is worth the trip.
