In nuclear physics, the working principle of an atomic bomb is based on which type of nuclear process?

Introduction / Context:
An atomic bomb is an extremely powerful explosive device that derives its destructive energy from nuclear reactions. In basic nuclear physics, it is very important to distinguish between fission, which is the splitting of heavy nuclei, and fusion, which is the joining of light nuclei. The question tests whether you remember which specific nuclear process, and which mode of control, is used in an atomic bomb as opposed to a peaceful nuclear reactor. Understanding this difference helps in separating concepts related to nuclear weapons and nuclear power plants.

Given Data / Assumptions:

• We are dealing with an atomic bomb, not a hydrogen bomb.
• Atomic bombs use heavy nuclei such as uranium 235 or plutonium 239.
• The focus is on the principle or basic working process of the device.
• Controlled and uncontrolled reactions are different ways of managing a chain reaction.

Concept / Approach:
An atomic bomb is based on a nuclear fission chain reaction. In nuclear fission, a heavy nucleus absorbs a neutron, becomes unstable, and splits into smaller nuclei, releasing energy and more neutrons. If these additional neutrons go on to split more nuclei without any control mechanism, the process rapidly accelerates. This fast, self sustaining chain reaction is called uncontrolled nuclear fission and results in a massive, explosive release of energy. In contrast, nuclear power reactors operate on controlled nuclear fission, where moderators and control rods regulate the rate of the chain reaction.

Step-by-Step Solution:
Step 1: Recall that an atomic bomb uses uranium 235 or plutonium 239 as fuel, both of which are fissionable materials.Step 2: When one such nucleus undergoes fission, it splits into smaller fragments and releases a large amount of energy and several neutrons.Step 3: These emitted neutrons strike other nearby nuclei, causing further fission events and releasing more neutrons.Step 4: In an atomic bomb, this chain reaction is not slowed down or regulated; it grows at an extremely rapid rate.Step 5: Because the reaction is uncontrolled, the energy release occurs in a tiny fraction of a second, producing an enormous explosion. This behaviour matches the description of uncontrolled nuclear fission.

Verification / Alternative check:
You can verify the answer by comparing atomic bombs with nuclear power reactors. Power reactors safely generate energy over long periods using controlled nuclear fission, whereas atomic bombs release energy almost instantaneously. Hydrogen bombs, on the other hand, are based mainly on nuclear fusion of light elements such as isotopes of hydrogen. Since the question clearly refers to an atomic bomb, not a hydrogen bomb, and to its primary operating principle, the only correct process is uncontrolled nuclear fission. This cross comparison confirms the answer.

Why Other Options Are Wrong:
Uncontrolled nuclear fusion is associated with thermonuclear or hydrogen bombs, not traditional atomic bombs, so option A is incorrect. Controlled nuclear fission is used in nuclear reactors to generate electricity safely, not in bombs, so option C does not match. Controlled nuclear fusion has not yet been achieved on a continuous, commercial scale and is not the principle behind atomic bombs, so option D is also incorrect. Only uncontrolled nuclear fission correctly describes the working process of an atomic bomb.

Common Pitfalls:
Students often confuse atomic bombs with hydrogen bombs and mix up fission and fusion. Another common mistake is to ignore the key words controlled and uncontrolled. Remember that whenever you see the term atomic bomb, you should think of heavy nuclei undergoing fission in an uncontrolled chain reaction. When you see hydrogen bomb or thermonuclear bomb, you should think of fusion. Carefully reading those adjectives in the options helps avoid such confusion in multiple choice questions.

Final Answer:
Uncontrolled nuclear fission