Q1. Which of the following radioactive particles has the least penetration power?
- Gamma rays
- Beta particles
- Alpha particles
- X-rays
Correct Option: 3. Alpha particles
Explanation: Alpha particles can be blocked by paper or skin, making them the least penetrating. Gamma rays and X-rays require dense materials like lead or concrete for shielding.
Q2. The harmful effects of ionizing radiation include all of the following EXCEPT:
- Cancer
- Mutations
- Shortened life-span
- Increased fertility
Correct Option: 4. Increased fertility
Explanation: Ionizing radiation decreases fertility and can cause cancer, mutations, and reduced lifespan.
Q3. Which of the following is a natural source of radioactive pollution?
- Nuclear power plants
- Cosmic rays
- Radiation therapy
- Atomic explosions
Correct Option: 2. Cosmic rays
Explanation: Cosmic rays and terrestrial radionuclides like Uranium-238 and Carbon-14 are natural sources. The rest are man-made.
Q4. The half-life of a radioactive substance refers to:
- Time required for half of the atoms to decay
- Time to double the radioactive energy
- Duration of human exposure
- Time taken to disappear from the body
Correct Option: 1. Time required for half of the atoms to decay
Explanation: Half-life is the time required for 50% of a radioactive substance to decay naturally.
Q5. Which of the following materials can effectively block gamma rays?
- Human skin
- Glass
- Paper
- Thick concrete
Correct Option: 4. Thick concrete
Explanation: Gamma rays are highly penetrating and require dense materials like thick concrete or lead for effective shielding.