Advertisements
Advertisements
प्रश्न
Why does thermionic emission not take place in non-conductors?
Advertisements
उत्तर
For thermionic emission, material should have low work function and large number of free electrons. But nonconductor does not have free electrons and they have higher work function. So, thermionic emission does not takes place in non-conductors.
APPEARS IN
संबंधित प्रश्न
Find the (a) maximum frequency and (b) minimum wavelength of X-rays produced by 30 kV electrons.
Would you prefer a material with a high work-function or a low work-function to be used as a cathode in a diode?
An isolated metal sphere is heated to a high temperature. Will it become positively charged due to thermionic emission?
A diode value is connected to a battery and a load resistance. The filament is heated, so that a constant current is obtained in the circuit. As the cathode continuously emits electrons, does it become more and more positively charged?
The cathode of a diode valve is replaced by another cathode of double the surface area. Keeping the voltage and temperature conditions the same, will the place current decrease, increase or remain the same?
The work function of aluminum is 4⋅2 eV. If two photons each of energy 2⋅5 eV are incident on its surface, will the emission of electrons take place? Justify your answer.
Emission of electrons by the absorption of heat energy is called ____________ emission.
Why do metals have a large number of free electrons?
Photoelectric emission is observed from a metallic surface for frequencies ν1 and ν2 of the incident light (ν1 > ν2). If the maximum value of kinetic energy of the photoelectrons emitted in the two cases are in the ration 1 : n then the threshold frequency of the metallic surface is ______.
Name the factors on which photoelectric emission from a surface depends.
What is responsible for electrical conduction in metals?
In the boundary-wall analogy, what does the metal surface represent?
In the boundary-wall analogy, what is the minimum push needed for a free electron to jump over the wall and come out?
What is the work function (\[\phi_0\]) of a metal?
Which unit is used for the work function?
Which particles at the surface hold free electrons inside the metal?
What causes field emission?
What is the order of the electric field required for field emission?
Which is an example associated with photoelectric emission?
