Most Repeated MDCAT Physics: Nuclear Physics MCQs

Explanation

Explanation:Equivalent dose (rem) = RBE factor × Absorbed dose (rad) Absorbed dose (rad) = Equivalent dose (rem) / RBE factor = 400 rem / 10 = 40 rad.1 rad = 0.01 J/kg.Total absorbed energy (J) = Absorbed dose (rad) × Mass (kg) × 0.01 J/kg/rad = 40 rad × 80 kg × 0.01 J/kg/rad = 32 J.

Explanation

Number of half-lives = 150 min / 25 min = 6 half-livesSimilarly, for element Y, with a half-life of 75 minutes, after 150 minutes, we can calculate the number of half-lives as follows:Number of half-lives = 150 min / 75 min = 2 half-livesFor element X: (1/2) ^ 6 = 1/64 For element Y: (1/2) ^ 2 = 1/4Therefore, the fraction of the number of nuclei of X remains unchanged to the number of nuclei of Y remains unchanged is:(1/64) / (1/4) = 1/64 * 4/1 = 1/16 This can be simplified to: 1:16So, the correct answer is option (a) 1:16.

Explanation

Option A: This option is incorrect. When a beta particle is emitted, the atomic number of the atom changes by one unit, but the mass number of the atom does not change. Option B: The correct answer is one unit; no units. When a beta particle is emitted, a neutron in the nucleus decays into a proton and an electron. The electron is emitted as a beta particle, and the proton remains in the nucleus. This changes the atomic number of the atom by one unit, since the number of protons is one more than the number of neutrons. The mass number of the atom does not change, since the mass of the electron is very small compared to the mass of the neutron or proton. Option C: This option is incorrect.

Explanation

The correct answer is a proton. A proton is a positively charged particle with a mass that is one fourth that of an alpha particle and a charge that is one half of an alpha particle, making it the particle described in the question.Beta particles are incorrect as they are negatively charged particles akin to electrons. Gamma rays are a form of electromagnetic radiation and do not have mass or charge. Neutrons have no charge, so they do not fit the description of a positively charged particle.

Explanation

This is the correct answer. Tritium is a radioactive isotope of hydrogen. It has one proton and two neutrons in its nucleus, making it the lightest radioactive element. Tritium undergoes beta decay, emitting an electron and becoming helium-3.Therefore, tritium is the lightest element that exhibits radioactivity.

Explanation

Radioactivity is the spontaneous emission of radiation in the form of particles or high-energy photons resulting from a nuclear reaction. It is also known as radioactive decay, nuclear decay, nuclear disintegration, or radioactive disintegration.

Explanation

Radiations are damaging to living organisms because cause ionisation of living cells. STB Pg-341 Hence, option A is correct.

Explanation

In beta positive decay, the number of electron is increased by one, but the number of nucleons i.e., neutrons and protons remain constant. Hence, option A is correct.

Explanation

This is the correct answer. Radioactivity is the spontaneous emission of radiation from the nuclei of unstable atoms. This radiation can take various forms, including alpha particles, beta particles, and gamma rays, which are all invisible to the human eye.

Explanation

Nuclear fusion in the sun involves the transformation of hydrogen into helium. This process increases the supply of helium as hydrogen nuclei (protons) are fused to form helium nuclei. Although nucleons are involved in this process, they are not increased in number, just rearranged. Positrons are indeed produced in small amounts during fusion, but they do not represent an increasing supply as helium does.

Explanation

Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay.So the correct option is A.

Explanation

An irreversible process can be defined as a process in which the system and the surroundings do not return to their original condition once the process is initiated.So the correct option is B.