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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
State three factors on which the rate of emission of electrons from a metal surface depends
What are free electrons?
State the energy conversion taking place in a cathode ray tube
Represent the change in the nucleus of a radioactive element when a β particle is emitted.
What happens if the negative potential is changed on a grid?
What is thermionic emission?
When is said to be the nucleus unstable?
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 Atomic number
What do you mean by Atomic mass
What kind of change takes place in a nucleus when a β -particle is emitted?
Draw a diagram of a simple atom showing the nucleus and electrons. In this atom:
(a) What type of charge will there be on the nucleus?
(b) What is the value of this charge?
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 characteristics of the substance used as thermionic emitter.
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?
What are cathode rays? Why are they called ‘cathode rays’? Name a material which exhibits fluorescence when cathode rays fall on it.
What do you understand by the term radioactivity?
Which part of the atom undergoes a change in the process of radioactive decay?
The half-life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours would be ______.
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 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)
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 ______.
A radioctive sample decays `7/8` times its original quantity in 15 minutes. The half-life of the sample is ______.
In the following atoms, which one is a radioisotope? Give one use of this isotope.
O16, C14, N14, He4
