A nucleus whose n/p ratio lies above the stability belt emits:

1. an alpha-particle
2. a beta-particle
3. alpha or beta particle
4. gamma rays
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Answer: B
Explanation:
• A nucleus that is above the stability belt emits beta-particle whereby a neutron is converted into proton. Thus n/p ratio decreases and the nucleus becomes more stable.
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Which one has greater n/p ratio?

1. ₆C¹⁴
2. ₇N¹⁴
3. ₈O¹⁷
4. ₁₂Mg²⁴
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Answer: A
Explanation:
• ₆C¹⁴ has greater n/p ratio i.e 8/6 = 1.33 and is untable.
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A nucleus whose n/p ratio lies below the stability belt emits:

1. an alpha-particle
2. a beta-particle
3. alpha or beta particle
4. gamma rays
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Answer: A
Explanation:
• A nucleus whose n/p ratio lies below the stability belt emits an alpha-particle and loses 2 protons and two neutrons. This increaes n/p ratio.
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In 1939, the nuclear fission reaction was discovered by:

1. Marie Curie
2. Henri Becquerel
3. James Chadwick
4. Otto Hahn and Fritz Strassmann
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Answer: D
Explanation:
• N/A
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The process of fission is always accompanied by:

1. formation of fission products
2. ejection of two or more neutrons
3. liberation of large amount of energy
4. all of these
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Answer: D
Explanation:
• N/A
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The fission reaction of U-235 occurs in --------- ways.

1. only one
2. about 10
3. about 35
4. about 5
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Answer: C
Explanation:
• A large nucleus can fission in many ways forming a variety of products.
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₉₂U²³⁵ undergoes fission on striking with a neutron to give the fission products:

1. ₅₆Ba¹³⁹ + ₃₆Kr⁹⁴ + 3₀n¹ + energy
2. ₄₂Mo¹⁰⁶ + ₅₀Sn¹²⁸ + 2₀n¹ + energy
3. ₅₆Ba¹⁴² + ₃₆Kr⁹¹ + 3₀n¹ + energy
4. all of these
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Answer: D
Explanation:
• A large nucleus can fission in many ways forming a variety of products.
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In the fission reaction, the mass of the products is:

1. equal to the mass of the reactant
2. less than the mass of the reactant
3. more than the mass of the reactant
4. none of these
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Answer: B
Explanation:
• A loss of mass of about 0.2 amu per uranium atom occurs and this mass is converted into a large quantity of energy.
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The minimum mass of a fissionable material required to sustain a fission chain reaction is called:

1. mass defect
2. critical mass
3. binding energy
4. supercritical mass
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Answer: B
Explanation:
• N/A
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For U-235 fission chain reaction, the critical mass is about:

1. 10 kg
2. 1 kg
3. 100 g
4. 0.5 kg
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Answer: A
Explanation:
• The critical mass varies for each fission chain reaction and for U-235, it is bout 10 Kg.
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