Atomic and Nuclear Physics

Einstein's famous equation E = mc² expresses the equivalence of mass (m) and energy (E), with c representing the speed of light in a vacuum. This shows that mass can be converted into energy and vice versa.

Energy in a nuclear reaction is produced due to a controlled chain reaction, where the rate of fission is carefully regulated to release energy steadily and safely, such as in nuclear reactors. Control rods and moderators adjust the number of neutrons available to sustain the reaction at a steady rate. An uncontrolled chain reaction leads to an exponential increase in fission events, causing a rapid and potentially destructive release of energy, as seen in nuclear weapons, not sustained energy production.

Gamma rays are a form of high-energy electromagnetic radiation emitted during a nuclear explosion and cause significant damage due to their high penetration power and ionizing effects on living tissue. Radio waves and 'Red Waves' do not cause such damage, and 'None of these' is incorrect since gamma rays are the primary damaging radiation.

Using Bragg's law nλ = 2d sinθ with n=1, d=2×10⁻¹⁰ m, and θ=30°, the wavelength λ = 2 × 2×10⁻¹⁰ × sin30° = 2 × 2×10⁻¹⁰ × 0.5 = 2×10⁻¹⁰ m. However, the question states 'glancing angle' which is complementary to θ, so θ = 90° - 30° = 60°. Using θ=60°, λ = 2 × 2×10⁻¹⁰ × sin60° ≈ 3.46×10⁻¹⁰ m, closest to option A (4×10⁻¹⁰ m). Therefore, option A is correct.

The photoelectric effect was explained by Albert Einstein, who proposed that light consists of quanta called photons, which can eject electrons from a metal surface. This explanation earned him the Nobel Prize in Physics in 1921.

An alpha particle ionizes an atom primarily through direct collision with the atom's electrons, knocking them out and creating ions. Electrostatic forces (attraction or repulsion) influence the interaction but ionization occurs mainly due to the direct impact.

Mass defect per nucleon is defined as the packing fraction, which represents the mass defect divided by the total number of nucleons. It is a measure of the average mass defect per nucleon in a nucleus.

Alpha particles consist of two protons and two neutrons, giving them a net positive charge of plus two. Therefore, the correct answer is 'Plus two'.

The mass of a neutron is approximately 1.67 x 10^-27 kilograms, which is close to the mass of a proton and much larger than the mass of an electron.

J.J. Thomson's atomic model, also known as the 'plum pudding model,' proposed that the atom is a uniform sphere of positive charge with electrons embedded within it, implying uniform density. Rutherford's and Bohr's models do not assume uniform density of the atom.

Pair production requires the presence of a heavy nucleus to conserve momentum, while energy and charge conservation are fundamental principles always upheld. Thus, net energy, net charge, and net momentum are all conserved during the process, making option D correct.

Pair production requires photons with energy greater than 1.022 MeV, which is typically found in gamma rays. X-rays generally do not have sufficient energy, and UV or IR rays have even lower energies, making gamma rays the correct choice.

Cadmium rods are used in nuclear reactors as control rods because cadmium has a high neutron absorption cross-section, which helps control the fission chain reaction by absorbing excess neutrons.

For a chain reaction to sustain and build up, the size of the radioactive target must be greater than the critical size. This ensures enough neutrons are produced and maintained to continue the reaction.

Neutrons and protons are collectively known as nucleons because they both reside in the nucleus of an atom. This term distinguishes them from other particles like mesons, bosons, or quartz, which are unrelated to nucleons.

Alpha particles, which are helium nuclei, interact with atoms primarily by ionizing them. This ionization process involves knocking out electrons from the atom, not protons or neutrons. Protons and neutrons are bound tightly within the nucleus and are not typically knocked out by alpha particles during ordinary encounters. Alpha particles have enough energy to remove electrons from atoms, causing ionization, but they do not generally dislodge nucleons (protons or neutrons) unless in specific nuclear reactions or high-energy collisions, which are not the usual context of the question.

The curie (Ci) is defined as 3.7 × 10^10 disintegrations per second, which is the standard unit of radioactivity. Option B correctly states this value.

The average distance an alpha particle travels in air before losing its ionizing power is called its 'range'. This term specifically refers to how far the particle can penetrate before it stops ionizing the medium.

A neutron is a subatomic particle with no net electric charge, meaning its charge is zero. This distinguishes it from protons (positive charge) and electrons (negative charge).

When nitrogen is bombarded with alpha particles, a nuclear reaction occurs producing an oxygen isotope and a proton. This is a classic example of a nuclear reaction where an alpha particle (helium nucleus) collides with nitrogen, ejecting a proton.

During the fusion of hydrogen into helium, nuclear reactions convert mass into energy, releasing a significant amount of energy. This is why stars, including the Sun, emit energy through fusion.

Nuclear forces, also known as strong nuclear forces, act between all nucleons—protons and neutrons—inside the nucleus. Therefore, they exist between proton-proton, proton-neutron, and neutron-neutron pairs, making 'All of the above' the correct answer.

Beta particles ionize atoms primarily through direct collisions with the electrons in the atoms. As high-energy electrons (or positrons), beta particles transfer part of their kinetic energy to orbital electrons during inelastic collisions, knocking these electrons out of the atom and causing ionization. This ionization is not mainly due to electrostatic attraction or repulsion but due to the energy transfer in collisions. Gravitational forces are negligible at atomic scales and do not contribute to ionization by beta particles.

During nuclear fission, the nucleus of an atom splits into smaller parts, releasing a large amount of nuclear energy. This energy originates from the strong nuclear forces within the nucleus.

The typical diameter of an atom is on the order of 10^-10 meters, which corresponds to option C. This is a well-established approximate size for atoms in physics and chemistry.