CBSE Physics Nuclear Physics Test 3 Online

1. Half-lives of two radioactive substances A and B are respectively 20 min. Initially, the samples of A and B have equal number of nuclei. After 80 min the ratio of remaining number of A and B nuclei is ?

2. Half-life period of a radioactive substance is 6 h. After 24 h activity is 0.01 μC, what was the initial activity ?

3. In one α and β-emission ?

4. The relationship between disintegration constant (λ) and half-life (T) will be ?

5. Which of the following is used as a moderator is nuclear reactors ?

6. A nuclear decay is expressed as

₆C¹¹ → ₅B¹¹ + β⁺ + X

Then the unknown particle X is ?

7. A free neutron decays into a proton, an electron and ?

8. A nucleus ruptures into two nuclear parts, which have their velocity ratio equal to 2 : 1. What will be the ratio of their nuclear size (nuclear radius) ?

9. Which of the following is positively charged ?

10. In nuclear fission process, energy is released because ?

11. The half-life of a radioactive material is 3 h. If the initial amount is 300 g, then after 18 h, it will remain ?

12. A sample of radioactive elements contains 4 x 101⁰ active nuclei. If half-life of element is 10 days, then the number decayed nuclei after 30 days is ?

13. Nuclear fission can be explained by ?

14. Complete the equation for the following fission process :

₉₂U²³⁵ + 0n¹ → ₃₈Sr⁹⁰ + .............. ?

15. Atomic weight of boron is 10.81 and it has two isotopes ¹⁰₅B and ¹¹₅B. Then, the ratio of atoms of ¹⁰₅B and ¹¹₅B in nature would be ?

16. In a fission reaction

²³⁶₉₂U →¹¹⁷X + ¹¹⁷Y + n + n

the binding energy per nucleon of X and Y is 8.5 MeV whereas of ²³⁶U is 7.6 MeV. The total energy liberated will be about ?

17. Half-life of a radioactive substance is 12.5 h and its mass is 256 g. After what time, the amount of remaining substance is 1g ?

18. In compound X(n,α)→ ₃Li⁷, the element X is ?

19. A nucleus _nX^m emits on α and two β-particles. The resulting nucleus is ?

20. The count rate of Geiger Muller counter for the radiation of a radioactive material of half-life 30 min decreases to 5 S^-1 after 2 h. The initial count rate was ?

21. The activity of a radioactive sample is measured as 9750 counts/min. The decay constant is approximately ?

22. The most penetrating radiation out of the following is ?

23. Alpha particles are ?

24. M_p and M_n are masses of proton and neutron respectively. An element of mass m has Z protons and N neutrons, then ?

25. The stable nucleus that has a radius half that of Fe⁵⁶ is ?