(Solved): Introduction: A schematic drawing of the CRT is shown in Figure 1. The picture tubes used for old ...

Introduction: A schematic drawing of the CRT is shown in Figure 1. The picture tubes used for old television and computer screens are just more highly evolved versions of the cathode ray tube (CRT). The significant feature of these devices is a beam of electrons, which travels at high speed through a vacuum in a glass container. The electrons are obtained by 'boiling them off a cathode, which is heated to a high temperature by a filament similar to the ones in light bulbs. They are then accelerated (from left to right in Figure 1) through a potential difference \( V_{a} \) of several hundred volts, and are focused into a beam by the electron gun (Region I of Figure 1.) CRT's without their glass container are available in the lab for you to examine. Figure 1. Schematic dinaing of a cathode-Tay tube The speed of the electrons can be found by using the principle of conservation of energy. Assume that the electrons start out with nearly zero speed; then their kinetic energy after leaving Region \( I \) is \[ \text { (Final KE) }-\frac{1}{2} m v^{2}-(\text { Initial Potential Energy })-q V_{a}-e V_{n_{r}} \] where \( e \) is the charge and \( m \) the mass of an electron. This equation can be rearranged for the final velocity of the electrons as they leave Region I, \[ v_{x}-v-\sqrt{\frac{2 e V_{a}}{m}} . \] The electrons are moving horizontally as they leave the gun. Therefore the horizontal velocity component is \( v_{x}=v \), and the vertical velocity component is \( v_{y}=0 \). If no forces are exerted on the electrons in Regions II or III, they travel in a straight line and strike the fluorescent glass screen near the center, producing a small glowing spot. (The force of gravity has a negligible effect on the electrons over this short distance.) Physics 1201 Pre-Lab for LAB 2 However, if other forces do act on the electrons in either of these regions, the beam will be deflected from its original path. In this lab you will introduce an electric field (in Region II), which will produce a force on the electrons. The electric field will be produced by applying a voltage to the deflection plates (see Figure 1, Region II). However, if other forces do act on the electrons in either of these regions, the beam will be deflected from its original path. In this lab you will introduce an electric field (in Region II). which will produce a force on the electrons. The electric field will be produced by applying a voltage to the deflection plates (see Figure 1, Region II). For the calculations in this lab, you will need to know some of the dimensions inside the CRT. The following, are average values; the variation from one tube to another seems to be about \( \pm \) \( 15 \% \) I.ength of vertical deflection plates, \( \epsilon=0.018 \mathrm{~m} \) Distance between vertical deflection plates, \( \quad d=0.0025 \mathrm{~m} \) Distance from vertical deflection plates to screen, \( L-0.16 \mathrm{~m} \) Also, the accelerating voltage \( V_{a} \) for your (TRT is written on the front of the wood housing - a typical value is \( \mathrm{V}_{\mathrm{a}}-550 \) volts, lut your CRT nay be diffirenf! Other useful information: charge of the electron: \( a-t-1.60 \times 10^{-19} \mathrm{C} \) mass of the electron: \( m=9.11 \times 10^{-31} \mathrm{~kg} \) Problems: 1. If the accelerating voltage \( V_{n} \) were \( 2 . \overline{1} \) volts, what would be the speed of the electrons emerging from the gun? 2. Using the speed of the electrons you found in Problem 1 above, compute the time required for an electron to travel the \( 0.16 \) meter distance from the deflection plates to the screen. Then compute the deflection caused by gravity acting on the electron over this distance. Have your instructor check your work.