Choose the correct statements:
A. \( \alpha \)-particle close to the nucleus suffers large scattering.
B. Hydrogen atom consists of a single proton and a single neutron.
C. Chadwick discovered neutron.
D. In \( \gamma \)-decay, photons are emitted.
E. The nucleus force between two nucleons falls rapidly to zero as their distance is less than a few femtometers.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A, C and D only
(A) \( \alpha \)-particle close to the nucleus suffers large scattering. — Correct. An α particle that passes very close to the small, heavy, positively charged nucleus feels a strong Coulomb repulsion and is deflected through a large angle, as in Rutherford’s scattering experiment.
(B) Hydrogen atom consists of a single proton and a single neutron. — Incorrect. An ordinary hydrogen atom has one proton in the nucleus and one electron outside it, and no neutron.
(C) Chadwick discovered neutron. — Correct. James Chadwick discovered the neutron in 1932.
(D) In \( \gamma \)-decay, photons are emitted. — Correct. A nucleus in an excited state drops to a lower level and gives out the energy as a γ-ray photon.
(E) The nucleus force between two nucleons falls rapidly to zero as their distance is less than a few femtometers. — Incorrect. The nuclear force is short-ranged: it falls rapidly to zero when the separation becomes more than a few femtometres. At smaller separations it is strong.
Note: Statements (A), (B), (C) and (E) of this question are from the latest textbook (2026-27). Statement (D), that photons are emitted in γ-decay, is printed only in the pre-rationalised textbook (2022-23). It was removed from the latest book, and it also appears to be out of the CUET 2026 syllabus.
NCERT (2026-27):
Alpha-Particle Trajectory – “… It is seen that an α-particle close to the nucleus (small impact parameter) suffers large scattering.”
Introduction – “… How could an atom as simple as hydrogen, consisting of a single electron and a single proton, emit a complex spectrum of specific wavelengths?”
Atomic Masses and Composition of Nucleus – “… Chadwick was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron.”
Nuclear Force – “… (ii) The nuclear force between two nucleons falls rapidly to zero as their distance is more than a few femtometres.”
NCERT (Pre-rationalised edition, 2022-23):
Gamma Decay – “… When a nucleus is in an excited state, it can make a transition to a lower energy state by the emission of electromagnetic radiation.”