Properties of Cathode Rays

Properties of Cathode Rays 

• Cathode rays are negatively charged.

J.Perrin showed that when cathode rays are passed through the poles of magnet these negatively charged particles deflect towards the positive pole of magnet.

J.J Thomson applied electric field on electrons.He found that when electrons passed through the electrically charged plates they are bend toward the positive charged plate.

These Experiments proved that electrons are negatively charged.

• Cathode rays produce greenish fluorescene on the walls of glass.When alumina placed in their path it glows red and ton stone glows yellow.
• They cast shadow when opaque object placed in their path.
• They produce Heat when they fall on the matter e.g when cathode rays from concave cathode are focussed on platinum foil it glows.
• Cathode rays drive small paddle wheel placed in their path.they possess momentum.It showed that cathode rays are not rays they are particles having definite mass and velocity.  
• The can ionize gases.
• They can cause a chemical change, because they have reducing effect.
• They can pass through thin metal foil like aluminium or gold foil.
• Cathode rays produce x-rays when they strike with anode particularly with large atomic mass.
• Their e/m value showed that they are simply electrons.

J.J Thomson concluded from his experiments that cathode rays consist of  streams of negatively charged particles.Stoney called these particle electrons.Thomson measured  e/m value of electrons.The e/m value remained same no matter which gas is used in discharged tube.