Science — UPSC Prelims practice questions

Question 1

Which of the following is/are correctly identified as applications of satellite remote sensing in India?
1. Forest cover mapping and monitoring deforestation
2. Assessment of flood damage
3. Mineral prospecting
Select the correct answer using the code given below. (A) 1 and 2 only (B) 2 only (C) 1 and 3 only (D) 1, 2 and 3

Accepted Answer

(D) 1, 2 and 3 — Correct. Indian remote sensing satellites are used for forest monitoring, flood assessment, and mineral prospecting among many other applications.

Question 2

Which of the following is commonly known as 'dry ice'? (A) Solid nitrogen (B) Solid carbon dioxide (C) Solid ammonia (D) Solid hydrogen peroxide

Accepted Answer

(B) Solid carbon dioxide — Correct. Dry ice is solid carbon dioxide (CO₂) at -78.5°C. It sublimates directly from solid to gas without passing through a liquid phase, hence the name 'dry' ice.

Question 3

Assertion (A): Cellulose is used in making shatter-proof glass.
Reason (R): Polysaccharides are not soluble in water.
Select the correct answer. (A) Both A and R are individually true and R is the correct explanation of A (B) Both A and R are individually true but R is not the correct explanation of A (C) A is true but R is false (D) A is false but R is true

Accepted Answer

(B) Both A and R are individually true but R is not the correct explanation of A — Correct. Cellulose derivatives (like cellulose acetate) are used as interlayers in laminated safety glass. Polysaccharides being water-insoluble is true but is not the reason cellulose is used in glass.

Question 4

With reference to the electromagnetic spectrum used in remote sensing, consider the following statements:
1. Microwave remote sensing can operate in all weather conditions including cloud cover.
2. Thermal infrared sensors measure the temperature of Earth's surface.
3. Visible light remote sensing requires sunlight and cannot operate at night.
Which of the statements given above are correct? (A) 1 and 2 only (B) 2 and 3 only (C) 1 and 3 only (D) 1, 2 and 3

Accepted Answer

(D) 1, 2 and 3 — Correct. Microwaves penetrate clouds for all-weather sensing, thermal IR sensors measure surface temperature from emitted radiation, and visible-light sensors require sunlight as they detect reflected solar radiation.

Question 5

Which of the following statements about LPG (Liquefied Petroleum Gas) is/are correct?
1. LPG primarily contains butane and propane.
2. A strong-smelling substance called ethyl mercaptan is added to LPG for leak detection.
3. LPG is lighter than air.
Select the correct answer using the code given below. (A) 1 and 2 only (B) 2 only (C) 1 and 3 only (D) 1, 2 and 3

Accepted Answer

(A) 1 and 2 only — Correct. LPG is a mixture of butane and propane, and ethyl mercaptan is added as an odorant for safety. However, LPG is heavier than air (its vapour density is about 1.5-2 times that of air), so statement 3 is incorrect.

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