Q100. Under Rutherford’s atomic model, which description best fits the nucleus?
[RRB Group D (20 August 2026, Shift 1)]
(A) A broad negatively charged region
(B) A tiny, dense, positively charged centre
(C) A diffuse neutral cloud
(D) A shell consisting only of electrons
Answer: (B) A tiny, dense, positively charged centre
Explanation: Rutherford inferred a compact central nucleus from the rare large-angle deflections of alpha particles passing through thin metal foil. Almost all atomic mass is concentrated in this extremely small, positively charged region, whereas electrons occupy the surrounding space.
Q99. Which observation in Rutherford’s alpha-scattering experiment supported the conclusion that atoms are mostly empty space?
[RRB Group D (14 August 2026, Shift 2)]
(A) Every alpha particle was absorbed
(B) The foil disintegrated
(C) Electrons carried a positive charge
(D) Only a small proportion of alpha particles were deflected
Answer: (D) Only a small proportion of alpha particles were deflected
Explanation: Most alpha particles travelled through the thin gold sheet almost undeflected. Consequently, most atomic volume could not contain dense matter. The few strongly deflected particles revealed a tiny central nucleus with concentrated positive charge and mass.
Q98. Which pair represents isobars?
[RRB Group D (10 August 2026, Shift 1)]
(A) Sodium-23 and magnesium-24
(B) Calcium-40 and argon-40
(C) Chlorine-35 and chlorine-37
(D) Carbon-12 and carbon-14
Answer: (B) Calcium-40 and argon-40
Explanation: Calcium-40 has 20 protons and argon-40 has 18. Despite the difference in atomic number, both nuclei contain 40 nucleons. The other same-element pairs are isotopes rather than isobars because their proton numbers coincide.
Q97. Which type of electric charge does a proton carry?
[RRB Group D (14 August 2026, Shift 3)]
(A) No charge
(B) Negative charge
(C) Variable charge
(D) Positive charge
Answer: (D) Positive charge
Explanation: A proton has one positive elementary charge, approximately 1.602 × 10⁻¹⁹ coulomb. Protons reside inside the atomic nucleus with neutral neutrons. The count of protons determines the atomic number and identity of each chemical element.
Q96. Approximately what is the radius of an atom in metres?
[RRB Group D (3 February 2026, Shift 3)]
(A) 10¹⁵
(B) 10⁻¹⁰
(C) 10¹⁰
(D) 10⁻⁵
Answer: (B) 10⁻¹⁰
Explanation: A typical atomic radius is on the order of one ångström, corresponding to 10⁻¹⁰ metre. The nucleus is much smaller, around 10⁻¹⁵ metre in radius, explaining why most of an atom is empty space.
Q95. Which experiment furnished evidence for the atomic nucleus?
[RRB NTPC Graduate CBT-I (17 March 2026, Shift 3)]
(A) Gold-foil scattering experiment
(B) Canal-ray experiment
(C) Cathode-ray experiment
(D) Oil-drop experiment
Answer: (A) Gold-foil scattering experiment
Explanation: Rutherford’s team directed alpha particles toward thin gold foil. Most passed through, but some underwent large deflections. The observations demonstrated that nearly all atomic mass and positive charge occupy a very small nucleus.
Q94. Who put forward the nuclear model after interpreting gold-foil scattering?
[RRB NTPC Graduate CBT-I (18 March 2026, Shift 3)]
(A) J. J. Thomson
(B) Niels Bohr
(C) John Dalton
(D) Ernest Rutherford
Answer: (D) Ernest Rutherford
Explanation: Ernest Rutherford proposed the nuclear model in 1911 after alpha-scattering measurements. His interpretation replaced Thomson’s positive-sphere model with a small, massive, positively charged centre. Bohr later introduced quantized electronic orbits to address atomic stability.
Q93. Which legislation approved in 2025 consolidated India’s civilian nuclear framework and permitted private participation?
[RRB NTPC Graduate CBT-I (22 March 2026, Shift 3)]
(A) Atomic Energy Reform Bill
(B) Civil Nuclear Governance Bill
(C) SHANTI Bill
(D) National Nuclear Expansion Bill
Answer: (C) SHANTI Bill
Explanation: The Sustainable Harnessing and Advancement of Nuclear Energy for Transforming India legislation, commonly called SHANTI, was designed to update the civil nuclear regulatory framework. The examination tested identification of the named law, not the physics of fission.
Q92. Under the SHANTI Act, 2025, which regulatory body was specified?
[RRB NTPC Graduate CBT-II (10 July 2026)]
(A) Atomic Energy Regulatory Board
(B) Nuclear Power Development Board
(C) Central Radiation Monitoring Board
(D) National Nuclear Safety Board
Answer: (A) Atomic Energy Regulatory Board
Explanation: The question identifies the Atomic Energy Regulatory Board as the nuclear oversight body associated with the SHANTI framework. Nuclear regulation concerns licensing, radiation protection and safety requirements rather than the production of electricity itself.
Q91. With which country did India announce a partnership on advanced and small modular reactors in February 2025?
[RRB NTPC Undergraduate CBT-I (8 May 2026, Shift 3)]
(A) France
(B) Japan
(C) Russia
(D) United States
Answer: (A) France
Explanation: India and France announced cooperation on advanced nuclear reactors and small modular reactor technologies. Such reactors aim for more flexible deployment of nuclear generation. The question tests a dated bilateral nuclear-technology agreement rather than a fundamental nuclear reaction.