Advertisements
Advertisements
प्रश्न
In a cathode ray tube state:
(i) the purpose of covering cathode by thorium and carbon.
(ii) the purpose of the fluorescent screen.
(iii) how is it possible to increase the rate of emission of electrons.
Advertisements
उत्तर
(i) The cathode is covered with thorium and carbon as it has low work function and it needs to be heated up to 2000 K to emit electrons. This serves it as a better electron emitter than tungsten.
(ii) The fluorescent screen helps in changing the electrical signal applied on the deflecting plates into the visual pattern on the screen.
(iii) The rate of emission of the electrons can be increased by
- Using a metal with a lower work function,
- Increasing the temperature of the surface of the metal, or
- Increasing the surface area of the metal emitting the electrons.
APPEARS IN
संबंधित प्रश्न
State three factors on which the rate of emission of electrons from a metal surface depends
When is said to be the nucleus unstable?
What do you mean by Atomic number
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?
Why should a radioactive substance not be touched by hands?
Why are materials of low work function preferred as thermionic cathode materials?
Name a common device where a hot cathode ray tube is used.
It is advised not to touch a radioactive substance by hand. Give reason.
Mention four properties of Becquerel rays.
