<p> Exploring Cathode Ray’s Particle Nature by Measuring its Mass to Charge Ratio (Based upon Thomson’s Experiments) Through a series of experiments, we have determined that Cathode Rays are composed of particles, not waves. The next step is to figure out whether the particles are molecules, atoms, or subatomic particles. To help, let’s figure out a way to measure the ratio of the particle’s mass to its charge. </p><p>Observations: We pass a cathode ray through a region between two parallel plates. In this region, there are two fields, an electric field pointing downward and a magnetic field pointing into the page. For a certain magnitude of the electric and magnetic fields, the ray passes straight through the region as illustrated in Figure A. If we increase the electric field relative to the magnetic field, the ray bends upward, as illustrated in Figure B. Likewise, if we increase the magnetic field relative to the electric field, then the ray bends downward as illustrated in Figure C. + + + + + + + + + + + + + + + + + +</p><p> q q q v v r v r m r m m E B E B E B ------Figure A Figure B Figure C</p><p> a) Model: Devise an explanation for your observations. Include diagrams and equations where appropriate. </p><p> b) Application: You observe the trajectory given in figure A when |E|= 465 N/C and |B| =1.55*10-4 T. How fast are the particles that makeup the ray moving? Next, we turn off the electric field so that only a magnetic field, |B|=1.55*10-4 T, acts on the particle. We observe the trajectory given in the figure below. </p><p>5 cm</p><p> q v m 1.2 cm</p><p> c) Model: Devise an explanation for this motion. Give appropriate free body diagrams, equations, etc. Is the shape of the trajectory parabolic or circular? </p><p> d) Application: Apply this model to calculate the ratio of the mass of the particle to its charge. Are the cathode rays composed of negatively charged Copper atoms that have a mass to charge ratio 1.659*10-7 kg/C, negatively charged proton-like particles with a mass to charge ratio of 1.044*10-8 kg/C, ionized Helium with a mass to charge ratio of 4.15*10-8 kg/C, or electrons with a ratio mass to charge ratio of 5.692*10-12 kg/C? </p>