Chapter 1, Problem 15P

In J. J. Thompson’s experiment depicted in Figures 1.10 and 1.11, assume that the electrons are initially traveling at a speed of $\text{8}.00\times \text{1}{0}^{\text{6}}{\text{m s}}^{-\text{1}}$ in the $+x$ direction and the electrostatic plates have a length of $\mathcal{l}=0.10\text{m}$ , between which the electrons are deflected toward the -y direction (downward) by an electric field of magnitude $\text{2}00{\text{ V m}}^{-\text{1}}$ . (Note that $\text{1 volt}=\text{1 V}={\text{1 J C}}^{-\text{1}}$ .) Calculate S, the magnitude of the downward displacement, if the fluorescent screen is located 0.90 m beyond the exit of the region between the two electrostatic plates. No magnetic field is applied to counteract the electrostatic force. (Caution: L is not 1.0 m nor 0.9 m; see Figure 1.11.)