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Justify with reason, whether the following nuclear reactions are allowed or not.
\[\ce{^A_Z X -> ^A_{Z - 2}X + ^4_{2}He}\]
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An electrons emitter must have how much work function and melting point.
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State three common properties of beta rays and cathode rays.
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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.
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Which part of the atom undergoes a change in the process of radioactive decay?
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From α, β and γ-rays, name the one which travels with the speed of light?
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From α, β and γ-rays, name the one which is not affected by electric or magnetic field?
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What is the value of the speed of gamma radiations in air or vacuum?
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Explain, why radium paint, consisting of zinc sulphide and a trace of radium salt, glows in the dark?
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State one use of radio-isotopes.
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It is advised not to touch a radioactive substance by hand. Give reason.
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State three ways of obtaining an electron-beam.
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Mention four properties of Becquerel rays.
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Mention one important function of ear main parts:
State the principle on which the functioning of a nuclear reactor is based.
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(a) Which one of the following graphs A or B shows free vibrations in a vacuum and which one shows free vibrations in a medium?
(b) How did you come to this conclusion.

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State one advantage of single movable pulley.
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The diagram below shows two parallel rays A (Orange) & B (Blue) incident from air, on air-glass boundary.

- Copy and complete the path of the rays A and B.
- How do the speeds of these rays differ in glass?
- Are the two refracted rays in glass parallel? Give a reason.
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A radioactive element is placed in an evacuated chamber. Then the rate of radioactive decay will ______.
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| Meera chose to use a block and tackle system of '9' pulleys instead of a single movable pulley to lift a heavy load. |
Why should she connect more number of pulleys in the upper fixed block?
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Complete the following radioactive reaction:
\[\ce{^-_-X -> ^-_-Y + ^4_2He -> ^234_91Z + ^0_-1e}\]
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