题干

如图S是发光点,S′是经凸透镜所成的虚像.

(1)画出入射光线SA的折射光线的位置.

(2)作图确定此透镜的焦点.

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答案(点此获取答案解析)

解:由于S'是S通过凸透镜所成的像,所以入射光线SA经透镜折射后也过S',根据像点和入射点画出折射光线;然后过S点作平行主光轴的光线,根据像点和入射点确定折射光线的位置,并且折射光线与主光轴的交点就是焦点;最后根据透镜的两个焦点关于透镜光心对称的特点确定另一个焦点的位置;如图所示:

同类题3

根据短文内容,从短文后的七个选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

Writing A Letter To Your Future Self

    Just imagine writing a letter to your future self 5 years from now, then opening it at that exact moment to see how much of it has come true. ____

    As you read the letter in the future, you can assess how many things agree with your expectations in the past. ____ Often times, the goals we set and our goal achievement process are affected by a lot of changes along the way. The letter lets you recognize how your current idea differs from the past.

    In addition to that, at the very moment you are writing the letter, your thoughts are stored right there in those words. When you open the letter in the future, you as your future self gets to compare how you used to be in the past with how you are now.  ____. It's very interesting to do so.

    Take out a pen and paper right now and start writing your letter to your future self. Set a time period to write to. ____ Then start writing. Think about the type of person you will be, your place in life, what you will have realized then, and so on.

    ____ Put it in a safe space where no one can find it. When you open this sometime in the near future, you might gain additional insights(了解) about yourself and your journey in the past few years.

A. And you can think about why that's the case.

B. It is a useful tool to be used in goal achievement.

C. Imagine how you will be like during that time period.

D. If you haven't, join me in writing a letter to yourself.

E. This lets you see how much things have changed since then.

F. At the end of the letter, write the date to open it on the cover.

G. It wasn't until we moved into our new house that I found it again.