tailieunhanh - IELTS reading and writing part 1

Tham khảo tài liệu 'ielts reading and writing part 1', ngoại ngữ, toefl - ielts - toeic phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Reading Passage 1 You should spend about 20 minutes on Questions 1 - 15 which are based on Reading Passage 1. The Birth Of The Microwave A Chances are you ll use a microwave oven at least once this week - probably according to research for heating up leftovers or defrosting something. Microwave ovens are so common today that it s easy to forget how rare they once were. As late as 1977 only 10 of U. S. homes had one. By 1995 85 of households had at least one. Today more people own microwaves than own dishwashers. B Magnetrons the tubes that produce microwaves were invented by British scientists in 1940. They were used in radar systems during World War fl and were instrumental in detecting German planes during the Battle of Britain. These tubes - which are sort of like TV picture tubes - might still be strictly military hardware if Percy Spencer an engineer at Raytheon a . defense contractor hadn t stepped in front of one in 1946. He had a chocolate bar in his pocket when he went to eat it a few minutes later he found that the chocolate had almost cocrpletely melted. That didn t make sense. Spencer wasn t hot -how could the chocolate bar be He suspected the magnetron was responsible so he tried an experiment. He put a bag of popcorn kernels in the tube. Seconds later they pepped. The next day Spencer brought eggs and an old tea - kettle to work. He cut a hole in the side of the kettle put an egg in it and placed it next to the magnetron. Just as a colleague went to see what was happening the egg exploded. 0 Spencer shared his discovery with his employers at Raytheon and suggested manufacturing magnetron - powered ovens to sell to the public. Raytheon was interested. They had the capacity to produce 10000 magnetron tubes per week but with World War 11 over military purchases had been cut down to almost nothing. What better way to recover lost sales than to put a radar set disguised as a microwave oven in every American home Raytheon agreed to back die project. The