弗兰克-赫兹实验物理分析新视角

New perspectives on the physics analysis of Frank-Hertz experiment

弗兰克-赫兹实验的板极电流是积分实验量,不能准确描述弗兰克-赫兹管中热电子能量分布和能量交换规律.采用仿I-V分析法引入弗兰克-赫兹管等效电阻,可直观地体现热电子与管中原子能量交换的共振吸收物理图象.认为管中热电子运动犹如江水奔流"后浪推前浪",在一系列不同G2栅极电位条件下,改变减速电压VG2P测量微分板极电流,深入分析热电子"重聚—共振"周期规律的物理原理.实验发现,处于能量交换区共振激发而失去动能的电子在管中形成负电本底且部分屏蔽G2栅极电场的加速作用.这一现象不仅导致其他电子需要比预期更高VG2K才能获得足以共振激发的能量,而且延缓了下次电子重聚进程.

The plate current of Frank-Hertz experiment is an integral measurement quantity,which cannot accurately describe the energy distribution of the electrons and the energy exchange between electron and atom in the Frank-Hertz tube.The equivalent resistance of Frank-Hertz tube was introduced by imitating the I-V analysis method,which could more intuitively reflect the resonance absorption principle of the energy exchange between electron and atom in the tube.It was considered that the movement of electrons in the tube was like a running river,the back water waves pushed forward.For a series of different G2 grid voltages,the decelerating voltage VG2 Pwas changed to measure the differential plate current,and the physical principle of the periodic process of grouping-resonance was thoroughly analyzed.It was found that the electrons,which lost kinetic energy due to resonance excitation in the energy exchange region,formed a negative electric field background and partially shielded the acceleration of G2 grid.This phenomenon not only caused higher VG2 Kthan expected to obtain enough energy for resonance excitation,but also delayed the next grouping process of electrons.