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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
What are free electrons?
Write one use of cathode ray tube.
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` ?
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.
Radiations given out from a source when subjected to an electric field in a direction perpendicular to their path are shown below in the diagram. The arrows show the path of the radiation A, B and C. Answer the following questions in terms of A, B and C.
1) Name the radiation B which is unaffected by the electrostatic field.
2) Why does the radiation C deflect more than A?
3) Which among the three causes the least biological damage externally.
4) Name the radiation which is used in carbon dating.
What happens to the atomic number of element when (i) An α -particle, (ii) A β -particle 1 and (iii) γ-radiation is emitted?
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?
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.
How is a cathode ray beam affected while passing through an electric field?
What are ‘Becquerel rays’?
Name the Different Radiations Which Are Emitted by the Radioactive Substances.
Are all the radiations mentioned by you, emitted in a single radioactive decay?
A certain nucleus has a mass number 20 and atomic number 9. Find the number of neutrons and protons present in it.
Two radioactive nuclei are represented by xAp and yAq and when p and q are mass numbers and x, y are the atomic number. How can the products be represented, i .e., what are the new values of p, q. x and y after the emission of an α-particle and a β-particle from A and B respectively.
What is the value of the speed of gamma radiations in air or vacuum?
Which of the following statements is/are correct?
- α particles are photons
- Penetrating power of γ radiation is very low
- Ionization power is maximum for α rays
- Penetrating power of γ radiation is very high
88Ra226 experiences three α - decay. Find the number of neutrons in the daughter element.
The half-life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours would be ______.
Two radioactive sources A and B of half lives of 1 hour and 2 hours, respectively, initially contain the same number of radioactive atoms. At the end of two hours, their rates of disintegration are in the ratio of ______.
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)
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 radioactive element is placed in an evacuated chamber. Then the rate of radioactive decay will ______.
When an α-particle of mass m moving with velocity ν bombards on a heavy nucleus of charge Ze, its distance of closest approach from the nucleus depends on m as:
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.
Why do the nuclei of some atoms undergo radioactive decay?
