Q1. What is the process by which an unstable atomic nucleus emits radiation in the form of particles or electromagnetic waves?
a) Nuclear fusion
b) Nuclear fission
c) Radioactivity
d) Atomic absorption
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Correct Answer: c) Radioactivity
Explanation: Radioactivity is the spontaneous emission of radiation from the nucleus of an unstable atom. This phenomenon occurs when the nucleus undergoes decay to attain a more stable configuration. The types of radiation emitted during radioactivity include alpha particles (helium nuclei), beta particles (electrons or positrons), and gamma rays (high-energy photons). Radioactive decay plays significant roles in various fields, including nuclear physics, medicine (radiation therapy and imaging), energy production (nuclear power), and carbon dating in archaeology. Understanding radioactivity is crucial for ensuring safety in handling radioactive materials and assessing their potential hazards.
Q2. Which of the following particles has the least penetrating power among the common types of radiation emitted during radioactive decay?
a) Alpha particles
b) Beta particles
c) Gamma rays
d) Neutrons
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Correct Answer: a) Alpha particles
Explanation: Alpha particles consist of two protons and two neutrons, making them relatively heavy and positively charged. Due to their mass and charge, alpha particles have the least penetrating power among the common types of radiation emitted during radioactive decay. They can be stopped by a few centimeters of air, a piece of paper, or even the outer layer of skin. However, alpha particles can be hazardous if ingested or inhaled, as they can cause damage to living tissues when emitted internally from a radioactive source.
Q3. Which radioactive decay process involves the emission of a helium nucleus?
a) Alpha decay
b) Beta decay
c) Gamma decay
d) Neutron decay
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Correct Answer: a) Alpha decay
Explanation: Alpha decay is a type of radioactive decay in which an unstable atomic nucleus emits an alpha particle, which is essentially a helium-4 nucleus consisting of two protons and two neutrons. During alpha decay, the atomic number of the parent nucleus decreases by two, while the mass number decreases by four. Alpha decay is commonly observed in heavy and unstable nuclei, such as those of uranium and thorium isotopes.
Q4. Which radioactive decay process involves the conversion of a neutron into a proton and the emission of an electron?
a) Alpha decay
b) Beta decay
c) Gamma decay
d) Neutron decay
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Correct Answer: b) Beta decay
Explanation: Beta decay is a type of radioactive decay in which an unstable atomic nucleus undergoes the conversion of a neutron into a proton, accompanied by the emission of an electron (beta particle) and an antineutrino or positron (depending on whether it is beta-minus or beta-plus decay, respectively). Beta decay occurs when the ratio of neutrons to protons in the nucleus is too high or too low, aiming to achieve a more stable neutron-to-proton ratio.
Q5. Which type of radiation has the highest penetrating power and can pass through most materials?
a) Alpha particles
b) Beta particles
c) Gamma rays
d) Neutrons
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Correct Answer: c) Gamma rays
Explanation: Gamma rays are a form of electromagnetic radiation with the highest penetrating power among the common types of radiation emitted during radioactive decay. They are highly energetic photons with no mass or charge, allowing them to penetrate most materials, including dense substances like lead and concrete. Gamma rays require thick shielding, such as dense metals or specialized materials, to attenuate their intensity effectively. Due to their penetrating power, gamma rays are widely used in medical imaging, radiation therapy, industrial radiography, and nuclear physics research.
Q6. Which of the following radioactive decay processes does not change the atomic number of the parent nucleus?
a) Alpha decay
b) Beta decay
c) Gamma decay
d) Neutron decay
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Correct Answer: c) Gamma decay
Explanation: Gamma decay, also known as gamma emission, is a type of radioactive decay that involves the release of gamma rays from an excited atomic nucleus following a previous decay process (such as alpha or beta decay). Unlike alpha and beta decay, gamma decay does not alter the atomic number or mass number of the parent nucleus. Instead, it results in the emission of high-energy photons (gamma rays) to transition the nucleus to a lower energy state.
Q7. Which type of radioactive decay involves the emission of an electron from the nucleus?
a) Alpha decay
b) Beta decay
c) Gamma decay
d) Neutron decay
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Correct Answer: b) Beta decay
Explanation: Beta decay is a type of radioactive decay in which an unstable atomic nucleus undergoes the conversion of a neutron into a proton, accompanied by the emission of an electron (beta particle) and an antineutrino or positron (depending on whether it is beta-minus or beta-plus decay, respectively). The emission of the electron from the nucleus leads to a change in the atomic number of the parent nucleus.
Q8. Which radioactive decay process involves the spontaneous disintegration of a neutron within the nucleus?
a) Alpha decay
b) Beta decay
c) Gamma decay
d) Neutron decay
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Correct Answer: d) Neutron decay
Explanation: Neutron decay, also known as neutron emission or neutron radioactivity, is a rare type of radioactive decay in which an unstable atomic nucleus spontaneously emits a neutron. This process occurs primarily in neutron-rich nuclei, aiming to achieve a more stable neutron-to-proton ratio. Neutron decay results in the formation of a new nucleus with a lower mass number and an unchanged atomic number.
Q9. What term describes the time required for half of the radioactive nuclei in a sample to undergo radioactive decay?
a) Decay constant
b) Half-life
c) Radioactive period
d) Emission duration
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Correct Answer: b) Half-life
Explanation: Half-life is the term used to describe the time required for half of the radioactive nuclei in a sample to undergo radioactive decay. It is a characteristic property of each radioactive isotope and is independent of the initial quantity of the sample. Half-life is commonly denoted by the symbol “t½” and is used to quantify the rate of radioactive decay and the stability of radioactive isotopes in various applications, including dating geological materials, medical imaging, and radiation therapy.
Q10. Which of the following factors does not affect the rate of radioactive decay of a substance?
a) Temperature
b) Pressure
c) Presence of catalysts
d) Initial concentration of the substance
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Correct Answer: b) Pressure
Explanation: Pressure does not significantly affect the rate of radioactive decay of a substance. Radioactive decay is a spontaneous process governed by the inherent instability of radioactive nuclei, and it is not influenced by external factors such as pressure. However, factors such as temperature, presence of catalysts, and initial concentration of the substance can affect the rate of radioactive decay by altering the probability of nuclear interactions and the energy barriers associated with the decay process.