UPSC Prelims 2010 Q34: Science & Technology – Physics
India - based Neutrino Observatory is included by the Planning Commission as a mega
science project under the 11th Five - Year Plan. In this context, consider the following statements:
1. Neutrinos are chargeless elementary particles that travel close to the speed of light.
2. Neutrinos are created in nuclear reactions of beta decay.
3. Neutrinos have a negligible, but non - zero mass.
4. Trillions of Neutrinos pass through human body every second.
Which of the statements given above are correct?
- (a) 1 and 3 only
- (b) 1, 2 and 3 only
- (c) 2, 3 and 4
- (d) 1, 2, 3 and 4
Answer: (d) 1, 2, 3 and 4
Explanation
Checking four statements about neutrinos
Neutrinos are subatomic particles central to the India-based Neutrino Observatory (INO) project.
| Statement | Verdict | Reason |
|---|---|---|
| 1. Chargeless, travel close to light speed | Correct | Neutrinos are indeed electrically neutral and move at speeds close to that of light |
| 2. Created in nuclear beta-decay reactions | Correct | Beta decay is a major natural source of neutrino production |
| 3. Negligible but non-zero mass | Correct | Neutrinos were once thought massless, but experiments confirmed they have a tiny but non-zero mass |
| 4. Trillions pass through the human body every second | Correct | Due to their extremely weak interaction with matter, trillions of neutrinos (mostly from the Sun) pass harmlessly through every person every second |
Neutrino facts:
| Point | Detail |
|---|---|
| Charge | Neutral (chargeless) |
| Mass | Tiny but non-zero |
| Interaction | Extremely weak, passes through matter almost undetected |
Answer: (d) 1, 2, 3 and 4.
Why each option is right or wrong
- (a) Incorrect. Statements 2 and 4 (beta decay origin, trillions passing through the body) are also correct, so '1 and 3 only' is too narrow.
- (b) Incorrect. Statement 4 (trillions passing through the body) is also correct, so '1, 2 and 3 only' is incomplete.
- (c) Incorrect. Statement 1 (chargeless, near-light-speed) is also correct, so '2, 3 and 4' wrongly excludes it.
- (d) CORRECT. All four statements accurately describe established neutrino properties and behaviour.
Key point
Neutrinos: chargeless, travel near light speed, produced in beta decay, have tiny non-zero mass, and trillions pass through the human body every second — all four statements are accurate.
Remember
Neutrinos: chargeless, near-light-speed, from beta decay, tiny non-zero mass, trillions pass through the body each second — all true.
Common mistakes
- Assuming neutrinos are completely massless, missing the confirmed tiny non-zero mass.
- Not knowing beta decay as a key natural neutrino source.
- Underestimating how harmlessly and constantly neutrinos pass through ordinary matter, including human bodies.
Exam tip
When a particle-physics question lists several accurate, non-contradictory facts about neutrinos, 'all of the above' is the likely answer.
Sources
- Tata Institute of Fundamental Research — India-based Neutrino Observatory: Project Report
- Frank Close — Neutrino (Oxford University Press, 2010)