单选题
如图8—10所示,A、B是置于真空中竖直放置的两块平行金属板,加电压U,一个带负电的粒子以初速度7.20由小孔水平射入两板中,粒子刚好可以到达B板,今把两板之间的距离缩小一半,仍要使粒子刚好到达B板,则粒子的初速度是(保持两极电压不变) ( )
- A、<img src="//wximg.233.com/attached/image/20130108/20130108160855065506.gif" alt="" border="0" />
- B、<img src="//wximg.233.com/attached/image/20130108/20130108160881658165.gif" alt="" border="0" />
- C、<img src="//wximg.233.com/attached/image/20130108/20130108160840804080.gif" alt="" border="0" />
- D、<img src="//wximg.233.com/attached/image/20130108/20130108160859965996.gif" alt="" border="0" />
参考答案 B