QUESTION: Which of these scientists is most closely associated with the laboratory apparatus shown below? A. John Dalton B. J.J. Thomson C. Ernest Rutherford D. James Chadwick - SCRIPT: Which of these scientists is most closely associated with the laboratory apparatus shown below? A. John Dalton B. J.J. Thomson C. Ernest Rutherford D. James Chadwick This is the apparatus that J. J. Thomson used. It’s called a cathode ray tube. Here’s the cathode, CLICK which is a piece of metal is subjected to a negative voltage. A beam, called a cathode ray, comes out of the cathode and travels to the other side of the tube, Which is coated with a material that lights up when hit by the cathode ray. CALLOUT fluorescent screen This particular tube is designed so that the cathode ray passes through a pair of metal plates. When a voltage is applied to the electrical plates, CLICK CLICK the cathode ray is bent toward the to the positive plate. This led to the conclusion that the cathode ray is stream of negatively charged particles. Since the same behavior is observed regardless of the material used for the cathode, it meant that these negatively charged particles are present in any atom. These particles are now called electrons. In other words, a cathode ray is essentially an electron beam. Modern versions of cathode ray tubes can be found in television sets and computer monitors (…not the flat panel kind). PAUSE CLICK PAUSE END RECORDING +

Video ID: 1-13-6 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08