Electric Discharge:
The passage of an electric current through a gas is called electric discharge.
Discharge Tube:
A hard glass tube along with the necessary arrangement, which is used to study the passage of electric discharge through gases at low pressure, is called a discharge tube.
Cathode Rays:
Cathode rays are the stream of negatively charged particles, electrons which are shot out at a high speed from the cathode of a discharge tube at pressure below 0.01 mm of Hg.
Work Function:
The minimum amount of energy required by an electron to just escape from the metal surface is known as work function of the metal.
W0 = f0 = hv0
Electron Emission:The minimum amount of energy required by an electron to just escape from the metal surface is known as work function of the metal.
Thermionic Emission:
Here electrons are emitted from the metal surface with the help of thermal energy.
Field or Cold Cathode Emission:
Electrons are emitted from a metal surface by subjecting it to a very high electric field.
Photoelectric Emission:
Electrons emitted from a metal surface with the help of suitable electromagnetic radiations.
Secondary Emission:
Electrons are ejected from a metal surface by striking over its fast moving electrons.
Forces Experienced by an Electron in Electric and Magnetic Fields:
a) Electric field: The force FE experienced by an electron e in an electric field of
strength (intensity) E is given by,
FE = eE
FE = eE
c) If the magnetic field is parallel to the direction of motion of electron, then, FB = 0.
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