题干

如图所示是一种液面升降监测装置原理图.点光源S发出的一束激光与水平液面成50°角射向平静的液面,则入射角为____°;光经液面反射后射到液面上方水平标尺上的S′点,当液面下降时,光点S′将____(选填“向左”、“向右”或“不会”)移动.

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40,向右

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    Sixteen is a special age in the United States. There's often a special celebration for a girl's 16th birthday---a big party called Sweet-16. It is like a wedding reception(结婚晚宴) in the number of guests and gifts handed out.

    About a month before the party, the girl's family sends out invitations to the guests. They must buy a special present for the birthday girl and the girl guests find good dresses to wear. A sweet-16 present usually costs $40 to $60. This is about $20 more than the usual-cost of a birthday present.

    The party itself is not held at someone's house. The hostess rents(租赁) a reception hall for the event. Food, cake and a DJ are provided. Around 6'clock, guests arrive and meet the birthday girl. Then the girl and her father have a special father-daughter dance. After that, guests dance for about 30 to 45 minutes.

    Then there is the most important part of the Sweet-16 party, the candle-lighting ceremony.

    The sweet-16 hostess stands behind 16 unlit(未点燃的) candles and dedicates(献给) each candle to her friends, family, and anything that she feels is important to her. A lot of crying and hugging goes on at this time.

    Afterwards, people sit and eat. Most guests begin leaving around 11 o'clock.

    This school year, I have been to two Sweet-16s. I am one of the youngest students in my grade (My birthday is in December). I'll have to wait another year before I can have my own special Sweet-16 party. I can't wait for it!