Nuclei Class 12 MCQs Questions with Answers

1. Boron rods in a nuclear reactor are used to

2. For a nuclear fusion process, suitable nuclei are

3. Radioactive substance emits

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

5. The process of radioactive radiations remains unaffected due to

6. An electron emitted in beta radiation originates from

7. The electrons cannot exist inside the nucleus because

8.  γ-rays are originated from

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

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

11.  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.

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

13. Nuclear forces exists between

14. 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?

15. Control rods used in nuclear reactors are made of

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

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

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

19. Fusion reactions take place at high temperature because

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