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प्रश्न
What is meant by radioactivity?
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उत्तर
Elements with a high atomic number such as uranium, thorium, radium have a property of spontaneously emitting invisible, highly penetrating and high energy radiation. This property is called radioactivity. The nucleus of radioactive elements is unstable.
संबंधित प्रश्न
When does the nucleus of an atom tend to become radioactive?
Answer the following questions based on a hot cathode ray tube.
State the approximate voltage used to heat the filament
How can they be made to leave the metal surface? (State any two ways)
A radioactive substance is oxidized. Will there be any change in the nature its radioactivity? Give a reason for your answer
Arrange α, β, and γ rays in ascending order with respect to their
1) Penetrating power.
2) Ionising power
3) Biological effect
Represent the change in the nucleus of a radioactive element when a β particle is emitted.
Under which conditions does the nucleus of an atom tend to radioactive?
What is thermionic emission?
State any two precautions to be taken while handling radioactive substances
Give one example of isobars.
Give a scientific explanation.
When the radiation coming out from a certain radioactive substance is passed through an electric field, marks are found at three places on the photographic plate placed in its path.
What do you mean by Mass number.
State the penetrating range of α, β and γ radiations.
What happens to the mass number of an element when (i) an α -particle, (ii) a β -particle, and (iii) γ -radiation is emitted?
A radioactive source emits three types of radiations. Name them.
(i) Name the radiations which are charged.
(ii) Name the radiations which are most penetrating.
(iii) Name the radiations which travel with the speed of light.
(iv) Name the radiations which have the largest mass.
Define the term radioactivity.
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?
Explain the use of radioactive in the field of medicine, agriculture and industry.
What are the uses of radioactive isotopes in following?
(a) Medical field,
(b) Agriculture,
(c) Industries?
A radioactive nucleus `""_"Z"^"A"` X first emits a beta particle and then an alpha particle to give the resulting nucleus `""_"Q"^"P"` Y What will be the values of P and Q in terms of A and Z?
State two properties that a substance should possess when used as a thermionic emitter.
Why are materials of low work function preferred as thermionic cathode materials?
What are ‘Becquerel rays’?
Justify with reason, whether the following nuclear reactions are allowed or not.
\[\ce{^A_Z X -> ^A_{Z + 1}Y + ^0_{-1}β}\]
What is the value of the speed of gamma radiations in air or vacuum?
It is advised not to touch a radioactive substance by hand. Give reason.
Unit of radioactivity is _______
The mean lives of a radioactive substance are 1620 and 405 years for β-emission and β-emission respectively. The time after which three fourth of a sample will decay if it is decaying both by β-emission and β-emission simultaneously will be ______ years.
(Take ln 2 = 0.693)
