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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
Answer the following questions based on a hot cathode ray tube.
State the approximate voltage used to heat the filament
What are free electrons?
Why do Free electrons not leave the metal surface on their own
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 the energy conversion taking place in a cathode ray tube
An electromagnetic radiation is used for photography in fog. [2]
(i) Identify the radiation.
(ii) Why is this radiation mentioned by you, ideal for this purpose ?
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 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?
Name two radioactive substances.
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?
A nucleus is \[\ce{^24_11 Na}\] β-radioactive.
Write the equation represent β-decay.
What are the types of emission?
How is a cathode ray beam affected while passing through a magnetic field?
What are cathode rays? Why are they called ‘cathode rays’? Name a material which exhibits fluorescence when cathode rays fall on it.
In a cathode ray tube state the purpose of the fluorescent screen.
An electrons emitter must have how much work function and melting point.
What is the value of the speed of gamma radiations in air or vacuum?
Explain, why radium paint, consisting of zinc sulphide and a trace of radium salt, glows in the dark?
State one use of radio-isotopes.
Mention four properties of Becquerel rays.
Unit of radioactivity is _______
The half-life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours would be ______.
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 ______.
In the following atoms, which one is a radioisotope? Give one use of this isotope.
O16, C14, N14, He4
