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प्रश्न
Why are materials of low work function preferred as thermionic cathode materials?
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उत्तर
By using materials of low work functions, the emission of electrons from such a surface takes place at relatively low temperature (at 1700°C in instead of 2500°C approximately).
संबंधित प्रश्न
What is thermionic emission?
What happens to the mass number of an element when (i) an α -particle, (ii) a β -particle, and (iii) γ -radiation is emitted?
In the following fig. shows a radioactive source S in a thick lead container. The radiations pass through an electric field between the plates P and Q. Complete the diagram to show the paths of α , β and γ radiations.
Why is the source S placed in a thick lead container?
What happens to the position of an element in the periodic table when it emits an alpha particle
State three safety precautions that you would take while handling the radioactive substances.
Define bound electrons.
What are cathode rays? Why are they called ‘cathode rays’? Name a material which exhibits fluorescence when cathode rays fall on it.
From α, β and γ-rays, name the one which travels with the speed of light?
A radioactive nucleus \[\ce{^A_ZX}\] undergoes spontaneous decay in the sequence \[\ce{^A_ZX -> _{Z-1 }B -> _{Z-3}C -> _{Z-2}D }\], where Z is the atomic number of element X. The possible decay particles in the sequence are ______.
Assertion (A): The force of repulsion between atomic nucleus and α-particle varies with distance according to inverse square law.
Reason (R): Rutherford did α-particles scattering experiment.
