1. Which statement is true for all three types of radioactive emission?
- They are deflected by electric fields
- They ionise gases
- They are completely absorbed by a thin aluminium sheet
- They emit light
Answer: They ionise gases
2. Radioactive material decays by simultaneous emission of two particles with respective half-lives 1620 and 810 years. The time, in years, after which one-fourth of the material remains?
- 1080
- 2430
- 3240
- 4860
Answer: 1080
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3. A 300-day old radioactive substance shows an activity of 5000 dps, 150 days later its activity becomes 2500 dps. What was its initial activity?
- 25000 dps
- 20000 dps
- 32000 dps
- 5000 dps
Answer: 20000 dps
4. What will happen in a time of 7 hours, if a radioactive substance has an average life of 7 hours?
- Half of the active nuclei decay
- Less half of the active nuclei decay
- More than half of the active nuclei decay
- All active nuclei decay
Answer: More than half of the active nuclei decay
5. The neutral atoms of all isotopes of the same element contain the same number of __________.
- neutrons only
- Electrons
- Mass numbers
- Masses
Answer: Electrons
6. A nuclide of the element plutonium 94 Pu 242. What is the number of neutrons in its nucleus?
- 242
- 336
- 148
- 94
Answer: 148
7. The electron emitted in β – radiation originates from where?
- Inner orbits of atoms
- Free electrons existing in nuclei
- The decay of a neutron in nuclei
- Photon escaping from the nucleus
Answer: The decay of a neutron in nuclei
8. A freshly prepared radioactive source of half-time 2h emits radiation of intensity which is 64 times the permissible safe level. Minimum time after which it would be possible to work safely with this source is which of the following?
- 6 h
- 12 h
- 24 h
- 20 h
Answer: 12 h
9. The atomic number is not changed by which type of radioactive decay?
- Beta
- Gamma
- Alpha
- delta
Answer: Gamma
10. Charge on α-particle is how many times the charge on proton:
- 4 times
- 2 times
- 3 times
- More than one of the above
Answer: 2 times
11. In radioactive decay which of the following quantity depends on the number of atoms:
- Half life
- Mean life
- Rate of decay
- Rate of decay and mean life
Answer: Rate of decay
12. What is the half-time of a radioactive sample (in minutes), if its mean life is 200 s?
- 0.69 min
- 2 min
- 2.57 min
- 2.31 min
Answer: 2.31 min
13. Isotopes of an element have a different number of
- Proton
- Neutron
- Electron
- atom
Answer: Neutron
14. The number of protons or atomic number is reduced to 2 by which form of radioactive decay?
- Beta-decay
- Gamma decay
- Alpha decay
- None of the above
Answer: Alpha decay
15. Which of the following substances cannot be emitted by radioactive substances during their decay?
- Protons
- Neutrinos
- Helium nuclei
- Electrons
Answer: Protons
16. Three types of radioactive elements are emitted when unstable nuclei undergo radioactive decay. Which of the following is not one of them
- Beta
- Gamma
- Alpha
- delta
Answer: delta
17. When two atomic nuclei combine it is called as
- Chain reaction
- Nuclear fusion
- Nuclear decay
- Nuclear fission
Answer: Nuclear fusion
18. Half-life of a radioactive element is 30 days, then the remaining amount after 90 days:
- 1/3
- 1/4
- 1/8
- 1/16
Answer: 1/8
19. A nuclear fission reaction becoming self-sustaining depends on
- electrons
- Neutrons
- Energy
- Protons
Answer: Neutrons
20. Charge on α-particle is how many times the charge on proton:
- 4 times
- 2 times
- 3 times
- equal
Answer: 2 times
21. Helium nuclei particles are called
- Gamma particles
- Beta particles
- Alpha particles
- No particles that are helium nuclei
Answer: Alpha particles
22. A beta particle is same as _______.
- an electron
- a proton
- a positron
- More than one of the above
Answer: an electron
23. A nucleus ZAX emits one α and two β particles. The resulting nucleus is
- Z−2A−4Y
- Z−4A−6Y
- ZA−4X
- More than one of the above
Answer: ZA−4X
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