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Radioactivity Questions

Practice 39 Radioactivity questions with detailed answers and explanations. Free MCQs, PYQs, and mock test questions for NEET, JEE, GATE, SSC and more.

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39
Total Questions
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5
Easy
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28
Medium
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6
Hard
Practice by Exam:Physics(35)Chemistry(3)PHYSICS(1)

About radioactivity — practice questions, PYQs & concepts

radioactivity is a frequently-tested topic on Physics, Chemistry, PHYSICS. ExamTest.live currently lists 39 radioactivity questions spanning previous-year papers from 2026 to 2026, each with worked solutions and a step-by-step explanation. Use the filters on this page to focus on a specific exam, difficulty level or year — every answer key is free, no sign-up required.

radioactivity weight in competitive exams

Across our radioactivity question bank, the largest sources are Physics (35), Chemistry (3) and PHYSICS (1). Click any exam chip above to drill down to that exam-specific question set.

How to use this page

  • Start easy: 5 easy radioactivity questions are available — build fluency before moving up.
  • Target weak years: Use the year filter to focus on the most recent 2026 paper or older PYQs you have not attempted.
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All Radioactivity Questions(1–39 of 39)

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Q1easymcqChemistryAIEEE2026
0% accuracy
The photon of hard gamma radiation knocks a proton out of nucleus to form:
Q2hardmcqPhysicsNEET (UG) 20172026
0% accuracy
Radioactive material 'A' has decay constant ' ' and material 'B' has decay constant ' '. Initially they have same number of nuclei. After what time, the ratio of number of nuclei of material 'B' to that 'A' will be ?
Q3mediummcqChemistryAIEEE 20072026
0% accuracy
A radioactive element gets spilled over the floor of a room. Its half-life period is . If the initial activity is ten times the permissible value, after how many days will it be safe to enter the room?
Q4mediummcqPhysicsAIEEE 20072026
100% accuracy
The half-life period of a radioactive element is same as the mean lifetime of another radioactive element . Initially they have the same number of atoms. Then:
Q5mediummcqPhysicsAIEEE 20072026
100% accuracy
In gamma ray emission from a nucleus:
Q6mediummcqPhysicsAIEEE 20062026
0% accuracy
The energy spectrum of -particles [number as a function of -energy ] emitted from a radioactive source is:
image
Q7easymcqPhysicsAIEEE 20032026
Which of the following cannot be emitted by radioactive substance during their decay?
Q8mediummcqPhysicsNEET 20212026
A radioactive nucleus undergoes spontaneous decay in the sequence:

The possible decay particles in the sequence are:
Q9mediummcqPhysicsNEET 20212026
A nucleus with mass number breaks into two fragments each of mass number . The binding energy per nucleon of unfragmented nuclei is while that of fragments is . The total gain in the Binding Energy in the process is:
Q10mediummcqPhysicsNEET 20212026
A half-life of a radioactive nuclide is hours. The fraction of original activity that will remain after hours would be:
Q11mediummcqPhysicsNEET 20222026
In the given nuclear reaction, the element is:
Q12mediummcqPhysicsNEET 20232026
The half-life of a radioactive substance is . In how much time, the activity of the substance drops to of its initial value?
Q13mediummcqPhysicsAIEEE2026
The intensity of gamma radiation from a given source is . On passing through of lead, it is reduced to . The thickness of lead which will reduce the intensity to will be:
Q14mediummcqPhysicsAIEEE2026
Starting with a sample of pure , of it decays into in . The corresponding half-life is:
Q15easymcqPhysicsNEET (UG) 20182026
For a radioactive material, half-life is minutes. If initially there are number of nuclei, the time taken (in minutes) for the disintegration of nuclei is:
Q16mediummcqPhysicsAIEEE 20032026
When nucleus originally at rest, decays by emitting an alpha particle having a speed , the recoil speed of the residual nucleus is:
Q17hardmcqPhysicsAIEEE 20032026
A nucleus with emits the following in a sequence: . The of the resulting nucleus is:
Q18mediummcqPhysicsAIEEE 20032026
A radioactive sample at any instant has its disintegration rate . After , the rate is . Then, the decay constant (per minute) is:
Q19mediummcqPhysicsAIEEE2026
A radioactive nucleus (initial mass number and atomic number ) emits -particles and positrons. The ratio of number of neutrons to that of protons in the final nucleus will be:
Q20mediummcqPhysicsFIITJEE AIEEE 2011 (Set Q)2026
The half life of a radioactive substance is . The approximate time interval between the time when of it has decayed and time when of it had decayed is:
Q21mediummcqPHYSICSNEET 20192026
The rate of radioactive disintegration at an instant for a radioactive sample of half-life is . The number of radioactive atoms in that sample at that instant is:
Q22mediummcqPhysicsNEET 20172026
Radioactive material ' ' has decay constant ' ' and material ' ' has decay constant ' '. Initially they have same number of nuclei. After what time, the ratio of number of nuclei of material ' ' to that of ' ' will be ?
Q23mediummcqPhysicsPhysics
0% accuracy
A nucleus emits one particle and two -particles. The resulting nucleus is:
Q24mediummcqPhysicsPhysics
0% accuracy
The half-life of a radioactive isotope is . It decays to another element which is stable. The two elements and were found to be in the ratio of in a sample of a given rock. The age of the rock was estimated to be:
Q25hardmcqChemistryChemistry
emits -particles and -particles. The neutron/proton ratio in the product nucleus is:
Q26mediummcqPhysicsPhysics
In radioactive decay process, the negatively charged emitted -particles are:
Q27mediummcqPhysicsPhysics
Two radioactive substances and have decay constants and respectively. At they have the same number of nuclei. The ratio of the number of nuclei of to those of will be after a time interval:
Q28hardmcqPhysicsPhysics
Two radioactive materials and have decay constants and respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of to that of will be after a time:
Q29mediummcqPhysicsPhysics
In the nuclear decay given below:

The particles emitted in the sequence are:
Q30easymcqPhysicsPhysics
The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an:
Q31hardmcqPhysicsPhysics
The activity of a radioactive sample is measured as at and at . The time (in minutes) at which the activity reduces to half its value is:
Q32mediummcqPhysicsPhysics
Two nuclei () and () decay to . When , the number of nuclei present is:
Q33mediummcqPhysicsPhysics
Half life is days. Time interval between when has decayed and has decayed is:
Q34mediummcqPhysicsPhysics
A mixture consists of two radioactive materials and with half-lives of and respectively. Initially the mixture has of and of . The amount of the two in the mixture will become equal after:
Q35mediummcqPhysicsPhysics
The half-life of a radioactive isotope 'X' is . It decays to stable element 'Y'. The ratio of 'X' to 'Y' in a rock is . The age of the rock is:
Q36mediummcqPhysicsPhysics
A radio isotope 'X' with a half life decays to 'Y' which is stable. A sample of the rock from a cave was found to contain 'X' and 'Y' in the ratio . The age of the rock is:
Q37easymcqPhysicsPhysics
A nucleus of uranium decays at rest into nuclei of thorium and helium. Then:
Q38hardmcqPhysicsPhysics
The half-life of a radioactive substance is . The time (in minutes) taken between decay and decay of the same radioactive substance is:
Q39mediummcqPhysicsPhysics
A radioactive material has a half-life of . What fraction of the material would remain after ?

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Radioactivity questions are commonly asked in Physics, Chemistry, PHYSICS. You can filter by exam using the links above.
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