题目

如图所示，OB是一束光线由水中射向空气时的反射光线，请在图中画出OB对应的入射光线和折射光线的大致方向并用箭头标出方向． 答案：解：由图可知，反射光线与水面的夹角为60°，则反射角等于90°﹣60°=30°，则入射角等于30°，根据反射角等于入射角，在法线右侧，水面下画出入射光线；过入射点在法线左侧的空气中画出折射光线，注意折射角大于入射角，如图所示： 根据句意，用括号中所给词的适当形式填空。1.—How old is your son?—We had a special party for his birthday last Saturday. (nine)2.The dictionary is very to us students.(help)3.Parents always tell their children not to accept any food from a .(strange)4.Don’t be angry with . He is just a child.(he)5.You should give up because it isn’t good for your health.(smoke)