What is Cathode or Emitter and Types of Cathode? The substance employed for electron emission is called a cathode or emitter. It is an essential part of an electron tube. The usefulness of a particular material as an emitter depends on (i) emission efficiency (ii) mechanical strength (iii) longevity at normal operating temperatures and (iv) …
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What is Photoelectric Emission and Laws of Photoelectric Emission?: When the surface of certain alkaline material such as sodium, potassium, cesium or rubidium is illuminated by a beam of light or ultraviolet radiations, the electrons are emitted. The phenomenon is called the photoelectric emission. The work function of the alkaline materials is very low and …
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Field Emission or Cold Cathode Emission: The metal piece can also be made to emit electrons by creating an high intensity electrostatic field near it. Such an emission of electrons is known as field emission or cold cathode emission. If an electrode (anode) having sufficiently high positive potential with respect to the metal piece (cathode) …
What is Secondary Emission? When a beam of high velocity electrons suddenly strikes a metallic surface, they give up their kinetic energy to electrons and atoms which they strike. Some of the bombarding electrons, called the primary electrons, collide directly with free electrons on the metal surface, and may knock them out from the surface, …
What is Thermionic Emission? A very common method used for electron emission is by heating the metal piece to a high temperature. The process of electron emission from the surface of metal into the surrounding space by heating the material is known as thermionic emission. As the temperature of the metal piece rises, a point …
What is Electron Emission? The liberation of electrons from the surface of a substance is known as electron emission. For electron emission, metals are employed because they have many free electrons. In a metal like copper, platinum or tungsten, there are plenty of free electrons. At room temperature these electrons are free only to the …
Electron Orbits and Energy Levels: As already discussed above electron orbits can occupy only certain rings or shells at fixed distances from the nucleus. These shells may be circular or elliptical and are numbered as K, L, M, N, O, P, and Q, K being nearest to the nucleus. Each shell can contain only a …
Explain Bohr’s Atomic Model: Bohr’s Atomic Model – Neils Bohr, a Danish physicist, put forward his model of atom in 1913. He retained Rutherford’s model of a very small positively charged nucleus at the centre. He also accepted the view that all the protons and neutrons (and hence most of the mass of the atom) …