In which of the following, emission of electrons does not take place?(a) Thermionic emission(b) X-rays emission(c) Photoelectric emission(d) Secondary emission
Answers
B
Thermionic emission: When a metal is heated to a high temperature, the free electrons gain kinetic energy and escape from the surface of the metal.
Secondary emission: When an electron strikes the surface of a metallic plate, it emits other electrons from the surface.
Photoelectric emission: Emission of electrons from the metal surface on irradiation with radiation of suitable frequency.
X-rays emission: High speed electrons (emitted from a filament) striking a target (a copper block) to emit X-rays
Answer:
(b) X-rays emission
Explanation:
Thermionic emission is the emission when the free electrons gain kinetic energy and escape from the surface of the metal asn and when a metal is heated to a high temperature.
When an electron strikes the surface of a metallic plate, it emits other electrons from the surface, the result produced is known as secondary emission. Whereas the emission of electrons from the metal surface on irradiation with radiation of suitable frequency causes a photoelectric emission.
In the case of X-rays emission, high speed electrons that are often emitted from a filament strike a copper target to emit X-rays.
Thus in X-rays the emission of electrons does not take place.