Practise 30 real Federal Board questions on Nuclear Physics from 2023 to 2026. See the answer and explanation as soon as you answer.
Nuclear Physics is one of the 14 main chapters in our Federal Board FSC Physics question bank (11th and 12th class), and about 6% of its real questions come from it. Tayyari Karo has 30 real questions on this chapter from 2023 to 2026; 9 are multiple choice and marked instantly, and the rest are short and long questions with a model answer. By difficulty: 21 medium, 7 easy, 2 hard.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
These are real past-paper questions. Think of your answer first, then open the explanation.
Which of the following is an example of nuclear fusion?
Answer: C. Energy production in the Sun
The Sun produces energy by fusing hydrogen nuclei into helium — nuclear fusion.
A hadron may either be a Baryon or a:
Answer: D. Meson
Hadrons are classified as baryons (3 quarks) or mesons (quark-antiquark pairs).
Which one belongs to Hadrons?
Answer: B. Pion
The pion is a meson, a type of hadron (built from a quark-antiquark pair); photon, electron and neutrino are not hadrons.
Which nuclear reaction is the source of energy in stars?
Answer: C. Fusion
Stars generate energy by fusing light nuclei (mainly hydrogen into helium) — nuclear fusion.
The time required for half of a radioactive sample to decay is called:
Answer: A. Half-life
Half-life (T½) is defined as the time taken for half of the radioactive nuclei in a sample to decay.
Average distance covered by an α-particle in air before its ionizing power ceases is called its:
Answer: B. Range
This distance is defined as the 'range' of the alpha particle in a given medium.
How do control rods and moderator play an important role in the action of nuclear reactor?
Moderators (e.g. graphite, heavy water) slow down the fast neutrons produced by fission to thermal (slow) speeds, since slow neutrons are much more effective at causing further fission in U-235 nuclei, sustaining the chain reaction.
Control rods (made of neutron-absorbing materials like cadmium or boron) are inserted into or withdrawn from the reactor core to absorb a controlled amount of excess neutrons, regulating the rate of the chain reaction to keep it steady (critical) for normal operation, or fully inserted to shut the reactor down in an emergency.
Differentiate between controlled and uncontrolled nuclear chain reactions. How is the chain reaction controlled?
In an uncontrolled chain reaction, each fission releases neutrons that cause more than one further fission on average, so the number of fissions (and energy released) grows exponentially and very rapidly — as in an atomic bomb.
In a controlled chain reaction, exactly one neutron from each fission (on average) goes on to cause another fission, keeping the reaction steady — as in a nuclear reactor.
Control method: control rods made of neutron-absorbing material (e.g. boron or cadmium) are inserted into or withdrawn from the reactor core to absorb excess neutrons, keeping the chain reaction just barely self-sustaining (critical, multiplication factor k=1) rather than growing uncontrollably.
| Session | Questions |
|---|---|
| 2026 Annual | 4 |
| 2025 1st Annual | 7 |
| 2025 2nd Annual | 7 |
| 2024 Annual | 6 |
| 2023 Annual | 6 |
30 real Federal Board (FBISE) Physics questions on Nuclear Physics from 2023 to 2026, for 11th and 12th class. Each one shows the session it came from.
No. We could not find an official FBISE marking scheme for these papers, so the answers and explanations are written by Tayyari Karo for practice. Check anything important with your teacher or textbook.
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