UPSC Prelims 2025 Q64: Science & Technology – Computer & Information Technology
- (a) I only
- (b) II only
- (c) Both I and II
- (d) Neither I nor II
Answer: (b) II only
Explanation
Wet-Bulb Temperature (WBT) = the temperature felt when sweat CANNOT evaporate due to high humidity.
When wet-bulb temperature exceeds 35°C → the human body CANNOT cool itself through sweating → leads to hyperthermia and death even in a shaded, resting individual.
| Statement | Claim | Verdict | Why |
|---|---|---|---|
| Statement I | Peninsular India will most likely suffer from flooding, tropical cyclones and droughts | FALSE | The World Bank report about wet-bulb temperatures exceeding 35°C is about extreme heat and humidity - not flooding or cyclones. The implication is heat stress, not flood risk. These are different hazard types. |
| Statement II | Survival of animals including humans will be affected as shedding body heat through perspiration becomes difficult | TRUE | This is the EXACT implication of WBT >35°C. At this level, sweating cannot cool the body because the air is already saturated with moisture. Heat cannot escape → fatal hyperthermia even for resting humans. |
Answer: (b) II only.
Wet-Bulb Temperature Science:
| WBT Level | Human Body Impact |
|---|---|
| Below 27°C | Safe for most activities |
| 27-32°C | Caution - heat stress for extended outdoor work |
| 32-35°C | Dangerous - prolonged exposure fatal |
| Above 35°C | UNSURVIVABLE even in shade - sweating useless, body overheats |
| India's risk | Indo-Gangetic plain and coastal areas approaching dangerous WBT levels |
Why each option is right or wrong
- (a) Incorrect. Statement I alone (flooding, cyclones, droughts) does not describe the implication of wet-bulb temperatures exceeding 35°C. Floods and cyclones are precipitation/storm events, unrelated to WBT.
- (b) CORRECT. Statement II correctly identifies that when WBT > 35°C, perspiration becomes ineffective and body heat cannot be shed — this is a direct, fatal physiological consequence.
- (c) Incorrect. Statement I describes climate hazards unrelated to wet-bulb temperature. WBT is specifically a heat-humidity index, not a predictor of flooding or cyclones.
- (d) Incorrect. 'Neither' would mean WBT >35°C has no implication for human survival — clearly wrong. Statement II is precisely correct about the thermophysiological consequence.
Key point
WBT >35°C = sweating cannot cool the body = fatal even at rest in shade. This is a heat-humidity hazard, NOT a flood or cyclone risk.
Remember
Wet-bulb temperature >35°C means sweating cannot cool the body — survival is impossible even at rest in shade. This is a heat-humidity hazard, not flooding or cyclones.
Common mistakes
- Associating wet-bulb temperature with flooding or cyclones — WBT is purely a heat-humidity measurement, not a precipitation or storm predictor.
- Not knowing why WBT matters: at 100% humidity, sweat cannot evaporate, so the cooling mechanism fails completely.
- Thinking WBT affects only outdoor workers — at WBT >35°C, even resting individuals in the shade cannot survive without cooling.
Exam tip
WBT = thermometer wrapped in wet cloth — it measures how well evaporation (sweating) can cool the air. WBT >35°C = fatal because sweating = useless at 100% humidity. India's risk zones: Indo-Gangetic plain + coastal regions. UPSC increasingly tests this climate-health nexus.
Sources
- World Bank Report — South Asia Hotspots: Climate Change and Human Survival
- NCERT Class XII — Geography (Climate Change and Human Health)