光线从空气中斜射入水中时,在水和空气的界面既发生反射,又发生折射,作出如图入射光线的法线、反射光线和折射光线。
Junk messaging has been a headache for years, __the action taken by the authori-ties has not yet produced the results expected
A.as
B.but
C.so
D.before
用气压计测量大气压时,能使气压计示数变小的是( )
A.把气压计从山顶拿到山脚下
B.天气由晴转阴雨
C.季节从夏季转到冬季
D.把气压计从室内拿到室外