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Topic Refraction of light
Asked 3 times across 2 UPSC exams over 5 years (2020–2025), peaking in 2025.
Key insights
- Most tested in NDA — 2 of 3 PYQs
- Most asked in 2025
- Recurs across 2 years (2020–2025)
How it travelled across exams
First appearance in each exam — the same idea, reframed.
CDS 2020 → NDA 2025
How the concept evolved
Rising — more than half its appearances (3 of 3) are since 2016.
Sample questions
You've seen the pattern — here are a few of the actual PYQs.
NDA2025
If the speed of light in carbon disulfide and vacuum is X and Y respectively, then
- A X < Y ✓
- B X > Y
- C X ≥ Y
- D X = Y
✓ Correct answer: (A)
Science & Technology › Physics & Chemistry
NDA2025
When a light ray passes through from air to water with a non-zero angle the ray will be
- A bending towards the normal ✓
- B bending away from the normal
- C propagating in straight line
- D reflected towards the opposite direction
✓ Correct answer: (A)
Science & Technology › Physics & Chemistry
CDS2020
If the speed of light in air is 3×10⁸ m/s, then the speed of light in a medium of refractive index 3/2 is
- A 2×10⁸ m/s ✓
- B 9/2×10⁸ m/s
- C 3/2×10⁸ m/s
- D 3×10⁸ m/s
✓ Correct answer: (A)
Science & Technology › Physics & Chemistry
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