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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.
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संबंधित प्रश्न
Name the radiations which are absorbed by greenhouse gases in the earth’s atmosphere.
An element `""_ZS^A` decays to `""_85R^222` after emitting 2 α particles and 1 β particle.
Find the atomic number and atomic mass of the element S.
State any two precautions to be taken while handling radioactive substances
What are isobars?
State the penetrating range of α, β and γ radiations.
What kind of change takes place in a nucleus when a β -particle is emitted?
What are the uses of radioactive isotopes in following?
(a) Medical field,
(b) Agriculture,
(c) Industries?
A radioactive substance is oxidized. What changes would you expect to take place in the nature of radioactivity? Explain your answer.
A radioactive source emits three types of radiations.
Name the radiation which has the highest ionizing power.
During the emission of a beta particle, the ______ number remains same.
What are the types of emission?
How is a cathode ray beam affected while passing through a magnetic field?
How is a cathode ray beam affected while passing through an electric field?
Why are materials of low work function preferred as thermionic cathode materials?
Name a common device where a hot cathode ray tube is used.
What do you understand by the term radioactivity?
What are ‘Becquerel rays’?
An electrons emitter must have how much work function and melting point.
From α, β and γ-rays, name the one which is not affected by electric or magnetic field?
State one use of radio-isotopes.
A radioactive material decays by simultaneous emissions of two particles with half-lives of 1400 years and 700 years respectively. What will be the time after which one-third of the material remains? (Take In3 = 1.1)
The activity of a certain radionuclide decreases to 15 percent of its original value in 10 days. What is its half life?
[ln (0.15) = -1.9]
Calculate the time interval between 33% decay and 67% decay if half-life of a substance is 20 minutes.
A radioactive element is placed in an evacuated chamber. Then the rate of radioactive decay will ______.
Complete the following radioactive reaction:
\[\ce{^-_-X -> ^-_-Y + ^4_2He -> ^234_91Z + ^0_-1e}\]
Assertion (A): Hydrogen atom consists of only one electron but its emission spectrum has may lines.
Reason (R): Only Lyman series is found in the absorption spectrum of hydrogen atom whereas in the emission spectrum, all the series are found.
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.
