Advertisements
Advertisements
Question
Why are materials of low work function preferred as thermionic cathode materials?
Advertisements
Solution
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).
RELATED QUESTIONS
A radioactive substance is oxidized. Will there be any change in the nature its radioactivity? Give a reason for your answer
In a cathode ray tube, what is the function of anode?
State any two precautions to be taken while handling radioactive substances.
An electromagnetic radiation is used for photography in fog. [2]
(i) Identify the radiation.
(ii) Why is this radiation mentioned by you, ideal for this purpose ?
A radioactive nuclide `""_86^226` Ra decays by emission of two alpha particles, one beta particle and gamma rays. Which of the following is the resulting nuclide X?
A certain nucleus A (mass number 238 and atomic number 92) is radioactive and becomes a nucleus B (mass number 234 and atomic number 90) by the loss of one particle.
What particle was emitted?
What are cathode rays? Why are they called ‘cathode rays’? Name a material which exhibits fluorescence when cathode rays fall on it.
Justify with reason, whether the following nuclear reactions are allowed or not.
\[\ce{^A_Z X -> ^A_{Z - 2}X + ^4_{2}He}\]
88Ra226 experiences three α - decay. Find the number of neutrons in the daughter element.
Two radioactive materials A and B have decay constants 25λ and 16λ respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of B to that of A will be "e" after a time `1/("a"lambda)` The value of a ______.
