![]() Thus, the oil droplets acquired negative charge Within this field (between charged metal plates), X-ray was used to ionise gas molecules which produced free electrons that attached themselves to the oil droplets.Millikan used an atomiser to spray droplets of oil into a chamber in which the oil droplets eventually would fall into a strong electric field.Robert Millikan utilised Newtonian physics and small oil droplets to determine the charge of an electron – a feat that Thomson could not previously achieve.This q/m ratio was crucial in showing that the atom is divisible and that cathode rays were subatomic particles - electrons.The q/m ratio of cathode rays to be 1800 times greater than for hydrogen ions (protons), meaning the mass of cathode ray particles is 1800 times smaller.This ratio was the same for all materials used.The charge/mass ratio was determined to be 1.76 x 10 11 Ckg –1.Equating the magnetic force to the electric force:.Thomson then removed the electric field and applied only the magnetic field, so that the cathode ray would deflect and the radius of the path could be physically determined.By equating the centripetal force and the force experienced by the magnetic field, he found:.When deflected by the magnetic field, it moves in the arc of a circle.When the particle is deflected by the electric field, it experiences a force F=qE.A fluorescent screen showed where the particle hit. He placed electric and magnetic fields at right angles to each other so that their forces would completely negate each other. Thomson used a modified version of a cathode ray tube.Thomson performed an experiment using cathode rays to determine the ratio of the charge of cathode rays to their mass.Experimental aim: Thomson, through this experiment, calculated the charge to mass ratio ( q/m) of cathode rays.It also showed that the ray was produced from the cathode.This supported the particle side of the controversy as electromagnetic waves are massless. When the glass wheel was struck by the cathode ray, the glass wheel slowly rotated, indicating that the cathode rays have momentum and therefore mass. ![]()
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