Question
Physics Question on Electromagnetic waves
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
Answer
X-rays emission
Explanation
Solution
Thermionic emission : When a metal is heated to a high temperature, the free electron 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 o felectrons from the metal surface on irradiation with radiation of suitable frequency
X-rays emission : They are due to transitions in the inner energy levels of the atom