如图，一玻璃工件的上半部是半径为R的半球体，O点为球心；下半部是半径为R、高为2R的圆柱体，圆柱体底面镀有反射膜．有一平行于中心轴OC的光线从半球面射入，该光线与OC之间的距离为0.6R．已知最后从半球面射出的光线恰好与入射光线平行（不考虑多次反射）．求该玻璃的折射率．

    Time is very important in our life. But it never had any importance in my life until I 1a watch from my father. It 2 me the importance of time in my life.

    I got this gift on a gray-sky day. I had to go to the 3 to pick up (接)my uncle Ali. However，I forgot it 4 I was playing with my friends. Later I  5 my uncle， but I was late for him. He had to 6 a taxi to my father's house.

    I got to my father's house 7. My father looked at me angrily. I said “Hi” to him and my 8 uncle. My father asked me to sit 9 him and gave me this watch which was a gift from 10. It was made of silver. Then he said，“Essa, did you have fun 11  your friends today? What you did was not very nice and you should be sorry for your 12 This watch will be a reminder（提醒物） for you. I hope today you have learned something  13 . ”

    I learned a lesson from my father: respect (尊重) time and 14 be late. The watch is important to me, not because of its 15 but because of the lesson（教训） that I learned from it.

原始大气的成分是：水蒸气、氢气、____ 、____、二氧化碳、硫化氢等．