Nuclei Class 12 MCQs Questions with Answers

1. The half-life period and the mean life period of a radioactive
element are denoted respectively by Th and Tm. Then

2. When a radioactive nucleus emits a (β-particle, the mass number of the atom

3.  Tritium is an isotope of hydrogen whose nucleus Triton contains 2 neutrons and 1 proton. Free neutrons decay into p + e¯+v¯. If one of the neutrons in Triton decays, it would transform into He3 nucleus. This does not happen. This is becauseTriton energy is less than that of a He3\ nucleus.

4. Control rods used in nuclear reactors are made of

5. Three specimens A, B, C of same radioactive element has activities 1 microcurie, 1 rutherford and 1 becquerel respectively. Which specimen has maximum mass?

6. An electron emitted in beta radiation originates from

7.  γ-rays are originated from

8. The electrons cannot exist inside the nucleus because

9. Boron rods in a nuclear reactor are used to

10. The half life of a radioactive susbtance is 30 days. What is the time taken to disintegrate to 3/4th of its original mass?

11. Samples of two radioactive nuclides A and B are taken λA and λB are the disintegration constants of A and B respectively. In which of the following cases, the two samples can simultaneously have the same decay rate at any time?

12. Radioactive substance emits

13. For a nuclear fusion process, suitable nuclei are

14. The quantity which is not conserved in a nuclear reaction is

15. The process of radioactive radiations remains unaffected due to

16. Fusion reactions take place at high temperature because

17. Nuclear forces exists between

18. A radioactive nucleus emits a beta particle. The parent and daughter nuclei are

19. When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom

20. Which of the following are not emitted by radioactive substances?