【单选题】关于光电效应的规律,下列说法中正确的是( )
A.
只有入射光的波长大于该金属的极限波长,光电效应才能产生
C.
发生光电效应的反应时间一般都大于10 -7 s
D.
发生光电效应时,单位时间内从金属内逸出的光电子数目与入射光强度成正比
【判断题】阅读理解,判断下列句子的正误 Sally spent much more time in singing and dancing than learning math. ( ) Sally was fourteen. She studied in a middle school. She liked dancing and singing and spent a lot of ti...
【判断题】阅读理解,判断下列句子的正误The father asked his sister to teach his daughter how to learn math. ( ) Sally was fourteen. She studied in a middle school. She liked dancing and singing and spent a lot o...
【单选题】Mark Zuckerberg, founder of Facebook, _________to donate a lot of money to charity when his daughter was born.