Free Radioactive Decay MCQs with Answers
82 Radioactive Decay MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Radioactive decay is the spontaneous transformation of unstable nuclei, described by decay constant, activity, half life and the exponential decay law. Work includes alpha, beta and gamma emissions, decay equations and remaining nuclei, with half life distinguished from the time required for complete decay.
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- A. a helium nucleus, two protons and two neutrons
- B. a fast electron
- C. a photon
- D. a proton
Explanation: Alpha emission therefore reduces the mass number by 4 and the atomic number by 2, moving the element two places back in the periodic…
Correct answer: a helium nucleus, two protons and two neutrons- A. decreases by 1
- B. increases by 1, while the mass number is unchanged
- C. decreases by 2
- D. is unchanged
Explanation: A neutron converts into a proton, an electron and an antineutrino, so the nucleus gains a proton while the total nucleon count stays the…
Correct answer: increases by 1, while the mass number is unchanged- A. Alpha
- B. Beta
- C. Gamma
- D. All are equal
Explanation: Gamma rays are uncharged electromagnetic radiation and need several centimetres of lead or a metre of concrete to attenuate them…
Correct answer: Gamma- A. a change in mass number only
- B. a change in atomic number only
- C. no change in either mass number or atomic number
- D. a change in both
Explanation: A gamma ray carries away energy from an excited nucleus without removing any nucleons, so the nuclide is the same afterwards, simply in a…
Correct answer: no change in either mass number or atomic number- A. Neutrons
- B. Neutrino
- C. Alpha particle
- D. Proton
Explanation: In beta decay, conservation of energy, momentum and lepton number requires emission of a neutrino or antineutrino along with the electron…
Correct answer: Neutrino- A. Due to the electrostatic force of attraction
- B. Due to the electrostatic force of repulsion
- C. Due to a direct collision
- D. Due to the gravitational force
Explanation: A beta-minus particle is an electron, so it repels the electrons bound in an atom through electrostatic repulsion and can knock them out…
Correct answer: Due to the electrostatic force of repulsion- A. Trajectory
- B. Range
- C. Firing level
- D. Limit
Explanation: The range of an alpha particle is the average distance it travels through air before losing enough energy that its ionising ability…
Correct answer: Range- A. Fast counting
- B. Extremely fast counting
- C. Slow counting
- D. All situations
Explanation: A Geiger counter is useful for ordinary or relatively slow counting because its recovery time, called dead time, prevents it from…
Correct answer: Slow counting- A. Rectilinear
- B. Curved
- C. Zig-zag or erratic
- D. Elliptical
Explanation: An alpha particle moving through matter repeatedly collides with atoms and is deflected, producing a short, zig-zag or erratic track…
Correct answer: Zig-zag or erratic- A. Protons
- B. Electrons
- C. Neutrons
- D. Nothing
Explanation: During an encounter, the positively charged alpha particle attracts an atomic electron and can transfer enough energy to remove it from…
Correct answer: Electrons- A. Fission reaction
- B. Fusion reaction
- C. Chain reaction
- D. Chemical reaction
Explanation: A fission chain reaction occurs when neutrons released by one fission event cause further nuclei to undergo fission.
Correct answer: Chain reaction- A. 3.74 x 10^9 disintegration per sec
- B. 3.70 x 10^10 disintegration per sec
- C. 3.55 x 10^10 disintegration per sec
- D. 3.60 x 10^10 disintegration per sec
Explanation: One curie is defined as 3.70 x 10^10 disintegrations per second, so the correct value is option b.
Correct answer: 3.70 x 10^10 disintegration per sec- A. 224 - 84
- B. 220 - 80
- C. 222 - 86
- D. 226 - 87
Explanation: An alpha particle contains 2 protons and 2 neutrons, so alpha emission reduces the mass number by 4 and the atomic number by 2: A = 226 -…
Correct answer: 222 - 86- A. α-rays
- B. β-rays
- C. γ-rays
- D. All of above have the same speed
Explanation: Gamma rays are electromagnetic radiation and travel at approximately 3.0 x 10^8 m/s in vacuum, whereas alpha particles are much slower and…
Correct answer: γ-rays- A. N=Noe-λt
- B. N=Noeλt
- C. N=Noe-λt/2
- D. No=N(1+eλt)
Explanation: Radioactive decay is exponential because the probability of decay per unit time is constant, giving N = N0e^-λt, where N and N0 are…
Correct answer: N=Noe-λt- A. X-rays
- B. B-rays
- C. γ-rays
- D. All have the equal penetrating powe
Explanation: Gamma rays have the greatest penetrating power among alpha, beta and gamma radiation because they are high-energy photons with no charge…
Correct answer: γ-rays- A. Greater than the critical size
- B. Less than the critical size
- C. Equal to the critical size
- D. All of above can build up a change reaction
Explanation: A chain reaction builds up only when the radioactive material is supercritical, which requires a target size greater than the critical…
Correct answer: Greater than the critical size- A. Beta particles
- B. Alpha particles
- C. Protons
- D. Gamma particles
Explanation: A Wilson cloud chamber is a radiation detecting chamber. It contains a supersaturated vaporized liquid that condenses around ions or…
Correct answer: Gamma particles- A. Neutron radiation
- B. Alpha radiation
- C. Gamma radiation
- D. All of them
Explanation: The release of radiation is a phenomenon unique to nuclear explosions. There are several kinds of radiation emitted; these types include…
Correct answer: All of them- A. Interference
- B. Polarization
- C. Absorption
- D. Diffraction
Explanation: Beta rays are high-speed electrons or positrons that are emitted from the nucleus during beta decay.
Correct answer: DiffractionRadioactive Decay MCQs: common questions
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There are 82 Radioactive Decay MCQs in the Physics bank, shown 20 to a page with the correct answer and an explanation on each.
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