Read the following passage and answer the questions.
Nuclear power stations and the sun both draw their energy from atomic nuclei. In a reactor, a neutron strikes a nucleus of uranium-235. The nucleus splits into two nuclei and a few neutrons. About 200 MeV of energy is released each time a uranium nucleus splits in this way. A reactor uses this energy to produce electricity. The sun works in a different way. In its core, very light nuclei, such as those of hydrogen, join to form heavier nuclei. These nuclei are positively charged and repel each other. So the joining takes place only at a very high temperature, where the nuclei move fast enough to come very close. Scientists are also trying to make light nuclei join in a controlled way on the earth.
Consider the following statements:
(A) For the same quantity of matter, a nuclear source gives about a million times more energy than a chemical source.
(B) The two nuclei formed when a uranium nucleus splits are nuclei of intermediate mass.
(C) The two nuclei formed when a uranium nucleus splits are stable nuclei.
(D) The enormous energy released in an atom bomb comes from controlled nuclear fission.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A) and (B) only
Nuclear energies are of the order of MeV per reaction, while chemical energies are of the order of eV.
(A) For the same quantity of matter, a nuclear source gives about a million times more energy than a chemical source. — True. An MeV is a million times an eV. For example, 1 kg of uranium gives about \( 10^{14}\ \mathrm{J} \), while 1 kg of coal gives about \( 10^{7}\ \mathrm{J} \).
(B) The two nuclei formed when a uranium nucleus splits are nuclei of intermediate mass. — True. Uranium-235 splits into a pair such as barium-144 and krypton-89, both in the middle range of mass numbers.
(C) The two nuclei formed when a uranium nucleus splits are stable nuclei. — False. These nuclei are radioactive. They change further, step by step, before stable end products form.
(D) The enormous energy released in an atom bomb comes from controlled nuclear fission. — False. The fission in an atom bomb is uncontrolled. So its energy comes out in one sudden explosion.
NCERT (2026-27):
Nuclear Energy – “… Thus for the same quantity of matter, nuclear sources produce a million times more energy than a chemical source. …”
Fission – “An example of fission is when a uranium isotope 23592U bombarded with a neutron breaks into two intermediate mass nuclear fragments …”
Fission – “… The fragment products are radioactive nuclei; they emit β particles in succession to achieve stable end products.”
Fission – “… The enormous energy released in an atom bomb comes from uncontrolled nuclear fission.”