Label the following statements about J. J. Thomson's cathode-ray tube experiments shown in Figure 2.6 as true or false. (f) By measuring the deflection of the cathode ray beam caused by electric fields of known strength, the charge-to-mass ratio of the electron was calculated.

Video transcript

welcome back everyone. We have a tour false example based on JJ's Thompson cathode ray tube experiments. The charge to mass ratio of the electron is calculated by measuring the deflection of the cathode ray beam by electric fields of known strength. So we want to think of our equation for charge to mass ratio E over M. Where E presents our charge of our electron. Recall that for the charge to mass ratio equation, Thompson decided to take the electrostatic deflection energy. So that's theta. E. Which is attributed from the magnetic plates. That consists of our Thompson's cathode ray tube where each of these electric plates carry a certain charge. We have a positively charged plate and a negatively charged plate. So this is from the electric plates. And he's dividing this electrostatic deflection energy by our magnetic deflection. Which in this case is our applied magnetic deflection which is squared. And this again is defined as are applied magnetic fields Or magnetic deflection. And what Thompson found from this equation is that our charge to mass ratio of an electron is equal to a value of negative 1.76 times 10 to the eighth power units of columns per gram. Now because we understand that this be square term represents our applied magnetic field. When we think of our setup of our cathode ray tube, we have a magnetic field that was directed towards our phosphor coated screen which produced a very bright light once the electric field hit that foss for screen. But recall that in the experiment some of these directed cathode beams were attracted to the positively charged electric plate. And so, because Thompson was able to measure this deflection of the cathode beams to the positively charged electric plates, that is how he was able to determine this value here for the charge to mass ratio of an electron. And so hopefully based on what I've covered, this was clear. But overall we can confirm that our statement given in the prompt is a true statement as our final answer. I hope everything I went through is clear. But if you have any questions, leave them down below and I'll see everyone in the next practice video.