Three-quarters of a radioactive sample decays in 10 minutes. What is its half-life?
Correct answer B. 5 minutes
Topic / 30 questions
Nuclear Physics MCQs
Nuclear Physics MCQs cover the composition of the nucleus, the spontaneous and random nature of radioactive decay, half-life and decay constant, and the biological effects and medical uses of radiation. They help MDCAT, ECAT and FSc candidates revise facts and short calculations, and every question on MCQs360 shows its correct answer instantly.
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Technetium-99m has a half-life of 6 hours. What percentage of an injected dose remains after 24 hours?
Correct answer D. 6.25%
A sample contains 2.0 × 10²⁰ radioactive nuclei with decay constant 1.5 × 10⁻¹⁰ s⁻¹. What is its activity?
Correct answer C. 3.0 × 10¹⁰ Bq
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What percentage of a radioactive sample has decayed after two half-lives?
Correct answer D. 75%
Uranium-238 (²³⁸₉₂U) decays through a series to stable lead-206 (²⁰⁶₈₂Pb). How many alpha and beta-minus particles are emitted in total?
Correct answer C. 8 alpha and 6 beta
Radium-226 (²²⁶₈₈Ra) decays by emitting one alpha particle. What are the mass number and atomic number of the daughter nucleus?
Correct answer D. A = 222, Z = 86
A radioisotope has a decay constant of 0.0231 per day. What is its half-life (T½ = 0.693/λ)?
Correct answer D. 30 days
The activity of a source falls from 800 Bq to 100 Bq. If its half-life is 6 hours, how long did this take?
Correct answer C. 18 hours
A 64 g sample of a radioisotope has a half-life of 2 hours. What mass of the isotope remains undecayed after 8 hours?
Correct answer C. 4 g
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What fraction of a radioactive sample remains undecayed after three half-lives?
Correct answer C. 1/8
Why are radioactive tracers used in medical diagnosis usually chosen to have short half-lives?
Correct answer C. So that the patient receives a small total radiation dose
A radioactive isotope has a half-life of 1386 s. What is its decay constant (λ = 0.693/T½)?
Correct answer C. 5.0 × 10⁻⁴ s⁻¹
How many neutrons are present in a nucleus of ²³⁸₉₂U?
Correct answer B. 146
How does ionising radiation mainly cause biological damage to living cells?
Correct answer B. By ionising molecules such as DNA, which can kill cells or cause mutations
What is the SI unit of equivalent (biological) radiation dose?
Correct answer D. Sievert
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Which radioisotope is widely used as a source of gamma rays for cancer radiotherapy?
Correct answer B. Cobalt-60
One becquerel (Bq) is equal to ____
Correct answer A. one decay per second
The decay constant λ of a radioactive isotope represents ____
Correct answer C. the probability per unit time that a nucleus will decay
The half-life of a radioactive isotope is the time taken for ____
Correct answer D. half of its undecayed nuclei to decay
When a nucleus undergoes beta-minus decay, what happens to its mass number and atomic number?
Correct answer C. A stays the same and Z increases by 1
About Nuclear Physics MCQs
Questions start with the structure of the nucleus: protons and neutrons, atomic and mass numbers, and counting neutrons in a given nuclide. Decay questions cover alpha, beta and gamma emission, the origin of the electron in beta-minus decay, and the spontaneous, random nature of decay that external conditions do not change. Half-life calculations ask how much of a sample remains after several half-lives and use λ = 0.693/T½ to convert between decay constant and half-life. The unit ends with how ionising radiation damages living cells and how radioisotopes are used in diagnosis and therapy.
Key facts to remember
- Mass number A = Z + N, where Z is the number of protons and N the number of neutrons.
- Decay constant and half-life: λ = 0.693/T½.
- After n half-lives, the undecayed amount is N = N₀(½)ⁿ.
- Alpha decay lowers A by 4 and Z by 2; beta-minus decay raises Z by 1 with A unchanged; gamma emission changes neither.
- In beta-minus decay, a neutron in the nucleus changes into a proton, an electron and an antineutrino.
- Radioactive decay is spontaneous and random and is not affected by temperature, pressure or chemical state.
Exams that include Nuclear Physics MCQs
Pakistan
- MDCAT
- ECAT (UET)
- NUMS
- AKU
- FSc boards
India
- NEET
- JEE Main
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Nuclear Physics MCQs
- For half-life questions, count the number of half-lives (t ÷ T½) and halve the amount that many times.
- Write each decay as a balanced equation, checking that A and Z add up on both sides.
- Remember that ionising radiation harms cells mainly by ionising molecules and damaging DNA.
- Learn a few medical uses: radiotherapy for cancer, iodine-131 for the thyroid and technetium-99m for diagnostic imaging.
Frequently asked questions
Which exams ask Nuclear Physics MCQs?
Nuclear Physics is part of the FSc physics syllabus, so its MCQs appear in MDCAT, ECAT (UET), NUMS and AKU entry tests and in FSc board papers. Students in India meet the same ideas in NEET and JEE Main, and Bangladeshi students in HSC and the medical admission test.
What is half-life?
Half-life is the time taken for half the radioactive nuclei in a sample to decay. It is constant for a given isotope and is linked to the decay constant by T½ = 0.693/λ. After two half-lives a quarter of the sample remains, and after three an eighth.
Last reviewed October 2026