Physics · Atoms and nuclei · chapter 13 of 14
Class 12 Physics Chapter 13: Nuclei Assertion-reason questions with answers
2 assertion-reason questions on Nuclei, each with its answer and the reason, written from the NCERT chapter. For the CBSE board, JEE Main and NEET, which are set from the same NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter. Each question gives an Assertion (A) and a Reason (R); choose how they stand to each other.
Question 1
Assertion (A): The density of the nucleus of 2713Al is nearly the same as that of 20882Pb. Reason (R): The nuclear radius varies as A1/3, so the volume of a nucleus is proportional to its mass number.
Show answer
Answer: (a) Both A and R are true, and R is the correct explanation of A.
Both are true. Since volume ∝ A and mass ∝ A, mass/volume does not depend on A: R explains A.
Question 2
Assertion (A): The binding energy per nucleon is nearly constant for nuclei with 30 < A < 170. Reason (R): The nuclear force between two nucleons does not depend on their electric charge.
Show answer
Answer: (b) Both A and R are true, but R is not the correct explanation of A.
Both are true, but the near-constancy comes from the short range of the nuclear force (saturation): an interior nucleon feels only its near neighbours, however large the nucleus. Charge independence does not explain it.
← Chapter 12: AtomsChapter 14: Semiconductor Electronics: Materials, Devices and Simple Circuits →