Advertisements
Advertisements
प्रश्न
What is meant by radioactivity?
Advertisements
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
Name a gas caused by the Greenhouse effect
What is thermionic emission?
A nucleus `""_11^24Na` emits a beta particle to change into Magnesium (Mg)
(i) Write the symbolic equation for the process.
(ii) What are numbers 24 and 11 called?
(iii) What is the general name of `""_12^24Mg `with respect to `""_11^24Na` ?
What do you mean by Atomic mass?
Give the relative ionizing power of α, β and γ radiations.
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 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?
State three safety precautions that you would take while handling the radioactive substances.
Why should a radioactive substance not be touched by hands?
State two characteristics of the substance used as thermionic emitter.
In a cathode ray tube state the purpose of covering cathode by thorium and carbon.
In a cathode ray tube state the purpose of the fluorescent screen.
How is a cathode ray tube used to convert an electrical signal into a visual signal?
Name a common device where a hot cathode ray tube is used.
What are ‘Becquerel rays’?
Justify with reason, whether the following nuclear reactions are allowed or not.
\[\ce{^A_Z X -> ^A_{Z + 1}Y + ^0_{-1}β}\]
It is advised not to touch a radioactive substance by hand. Give reason.
Mention four properties of Becquerel rays.
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 ______.
The count rate of activity of a radioactive sample of a very large population decreased from 1024 to 128 in 3 minutes. Then the rate of disintegration at the end of 5 minutes is ______.
In U238 ore containing Uranium the ratio of U234 to Pb206 nuclei is 3. Assuming that all the lead present in the ore is final stable product of U238. Half life of U238 to be 4.5 × 109 years and the age of ore is ______ × 109 years. (in 109 years)
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]
If 10% of a radioactive substance decays in every 5 years, then the percentage of the substance that will have decayed in 20 years will be ______.
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 ______.
A deuteron strikes 8O16 nucleus with subsequent emission of an alpha particle. Identify the nucleus so produced:
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.
