题目

在时究凸透镜成像规律时，将焦距为10cm的凸透镜和点燃的蜡烛固定在光具座上（如图），在光屏上得到了烛焰清晰的像（图中光屏未画出）。下列说法正确的是（ ）A．光屏上所成的是倒立、缩小的实像B．光屏上所成的是倒立、放大的实像C．光屏一定位于60~70cm刻度之间D．光屏一定位于70~90cm刻度之间 答案：【答案】AC【解析】AB．由题意知，凸透镜的焦距为10cm，由图可知物距为u=50.0cm-20.0cm=30.0cm因为物距u＞2f，在光屏上呈现倒立缩小的实像，故B错误，A正确；C．因为物距u＞2f，根据凸透镜成像的规律，像距大于1倍焦距，小于2倍焦距，即10cm＜v＜20cm所以，光屏一定位于60~70cm刻度之间，故D错误，C正确。故短文中共有10处错误，错误涉及一个单词的增加、删除或修改。增加：在缺词处加一个漏词符号(∧)，并在此符号下面写出该加的词。删除：把多余的词用斜线( \ )划掉。修改：在错的词下划一横线，并在该词的下面写出修改后的词。注意：1. 每处错误及其修改均仅限一词；2. 只允许修改10处，多者(从第11处起)不计分。Mark Twain, one of the best-known American writer in the 19th century, who was born in Missouri. His hometown lie on the banks of the Mississippi River, there he spent his childhood. When he grew up, he worked like a pilot on a river boat for some time. Mark Twain is his pen name. He took it from the shout of the sailors measure the depth of the water. Mark Twain wrote a lot of novels, but one of them is The Adventures of Tom Sawyer. It brought his fame and honor. Some of his writings have translated into many languages. He and his works are deep loved by readers throughout the world.