Physics & chemistry in everyday life

Answer: (a) 1 only

Only statement 1 is correct. Carbon fibre is a light, strong material used in vehicle bodies and in aircraft parts, and it can be recovered from used composites and reused, so it is not a one-time material.

• ✓ 1. Carbon-fibre composites go into vehicle chassis, body panels and doors, and into aircraft fairings, fuselages and floor panels. Their strength for low weight is the reason.
• ✗ 2. Carbon fibre can be recycled. Recycled fibre is already used in new products and needs far less energy than making virgin fibre, which is highly energy intensive.

Remember · Carbon fibre is strong and light, used in cars and aircraft, and is recyclable: recovered fibre is reused in new composites.

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) All three

All three actions need an accelerometer. An accelerometer is a sensor that measures changes in motion, and a crash, a free fall and a tilt each show up as a change in acceleration that the device can read.

• ✓ 1. Airbag systems decide whether to deploy from how abruptly the car's speed changes, which an accelerometer measures.
• ✓ 2. Drives in laptops use an accelerometer to sense free fall; the drive then parks its read-write head or powers down before impact to avoid damage.
• ✓ 3. A phone's accelerometer senses the direction of gravity, so it knows how the phone is tilted and rotates the display between portrait and landscape.

Remember · An accelerometer senses changes in motion. It triggers airbags, protects laptop drives in free fall and rotates phone screens.

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) Infrared waves are largely absorbed by water vapour that is concentrated in the lower atmosphere.

Statement (c) is correct: water vapour, ozone and other gases in the lower atmosphere (the troposphere) absorb much of the near-infrared radiation passing through. The other options misstate insolation values or the nature of infrared light.

• ✓ (c) NCERT says water vapour, ozone and other gases within the troposphere absorb much of the near-infrared radiation. Water vapour is concentrated in the lower atmosphere.
• ✗ (a) NCERT gives insolation at the surface as about 320 W/m2 in the tropics and about 70 W/m2 at the poles, a ratio of under five, and it says the equator receives less than the tropics. Ten times is far too high.
• ✗ (d) Infrared waves lie just beyond the visible spectrum; the human eye cannot see them. They are not part of the visible spectrum.

Remember · In the troposphere, water vapour, ozone and other gases absorb much of the near-infrared radiation. Insolation is about 320 W/m2 in the tropics and 70 W/m2 at the poles.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 8 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 8 (practise this chapter)

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error