题目

No visit to London is complete without checking out its fantastic selection of museums and galleries. Here are some of the best (in no particular order). Take your pick, then use the London attractions map to work out how to get there and which one to visit next.1. British MuseumBritish Museum has been displaying global historic artifacts discovered by British explorers. Opened in 1759, it was the first national museum to be open to the public in the world. Highlights include the Rosetta Stone, the Parthenon Sculptures and Egyptian mummies.Address: Great Russell St, WC1B 3DGPrice: Free (perman如图所示，空气中有一块截面为扇形的玻璃砖，折射率为，现有一细光束，垂直射到面上，经玻璃砖反射、折射后，经面平行于入射光束返回，∠为，圆半径为，则入射点距圆心的距离为