Science in Everyday Life — Practice Questions
UPSC Prelims-pattern practice questions on everyday science with full explanations — scattering, eye defects, fuels, blood groups and pH.
Questions
These are original UPSC-pattern practice questions. Attempt each one before revealing the answer.
Red light is used for danger signals because
Solution
Red has the longest wavelength in the visible spectrum and is scattered least by air, haze and fog, so it is visible from farthest away. Option A reverses the fact (blue is scattered most). Option C is wrong — violet has the shortest wavelength. Option D is wrong — the eye is most sensitive to yellow-green light.
Answer: B
Consider the following statements:
- A person with myopia can see nearby objects clearly but not distant ones.
- Myopia is corrected using a convex lens.
- Presbyopia arises mainly from the weakening of the ciliary muscles with age.
Which of the statements given above is/are correct?
Solution
Statements 1 and 3 are correct. Statement 2 is incorrect — myopia is corrected with a concave (diverging) lens; a convex lens corrects hypermetropia.
Answer: C
Consider the following statements:
- LPG consists mainly of methane.
- Ethyl mercaptan is added to LPG so that leaks can be detected by smell.
- CNG consists mainly of methane.
Which of the statements given above is/are correct?
Solution
Statements 2 and 3 are correct. Statement 1 is incorrect — LPG is mainly butane and propane; CNG is mainly methane. LPG has no smell of its own, so ethyl mercaptan is added as an odorant.
Answer: D
A person with which of the following blood groups is generally considered a universal donor of red blood cells?
Solution
O negative red cells carry no A, B or Rh antigens, so they are least likely to cause a reaction in any recipient. AB positive is the universal recipient (its plasma has no anti-A or anti-B antibodies). A negative and B positive cells carry antigens that would react in incompatible recipients.
Answer: A
Consider the following statements:
- Pure water at 25 °C has a pH of 7.
- Rain with a pH below 5.6 is called acid rain.
- Human blood is slightly acidic.
- Antacids used for acidity are bases.
How many of the statements given above are correct?
Solution
Statements 1, 2 and 4 are correct. Normal rain is slightly acidic (about 5.6) because of dissolved carbon dioxide, so only rain below that is termed acid rain. Statement 3 is incorrect — blood is slightly basic, at about pH 7.4. Three are correct.
Answer: C
Antimicrobial resistance is often called a “silent pandemic”. Explain how it develops and discuss the measures needed in India.
Solution
Introduction: Antimicrobial resistance (AMR) occurs when bacteria, viruses, fungi or parasites evolve to survive the drugs designed to kill them, making infections harder and costlier to treat. It spreads quietly, without the visible spikes of an outbreak — hence “silent pandemic”.
Body:
- How it develops: random mutations give some microbes survival advantages; antibiotic use kills susceptible microbes and leaves resistant ones to multiply; resistance genes can pass between bacteria.
- Drivers in India: over-the-counter sale of antibiotics; self-medication and incomplete courses; antibiotics for viral illnesses; use in poultry, livestock and aquaculture; discharge of pharmaceutical effluents; poor sanitation and infection control in hospitals.
- Measures taken: National Action Plan on AMR (2017) on the One Health approach; the Red Line campaign (2016) for prescription-only antibiotics; surveillance networks.
- Further measures: enforcement of prescription-only sale; antimicrobial stewardship in hospitals; vaccination and sanitation to prevent infections; limits on antibiotic use in animal farming; effluent standards for drug factories; incentives for new antibiotics and diagnostics; public awareness.
Conclusion: AMR threatens to undo a century of medical progress. A One Health approach — linking human, animal and environmental health — with strict stewardship is India’s best defence.