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Topic Reflection
Asked 10 times across 4 UPSC exams over 11 years (2015–2026), peaking in 2023.
Key insights
- Most tested in NDA — 5 of 10 PYQs
- Most asked in 2023
- Recurs across 7 years (2015–2026)
How it travelled across exams
First appearance in each exam — the same idea, reframed.
CDS 2015 → CAPF 2017 → NDA 2021 → CISF 2022
How the concept evolved
Rising — more than half its appearances (9 of 10) are since 2016.
Related concepts
Ideas UPSC tests alongside this one — keep exploring.
Sample questions
You've seen the pattern — here are a few of the actual PYQs.
NDA2026
A periscope uses two plane mirrors inclined at 45°. If the tube of the periscope is filled with a complete transparent liquid of refractive index 1·5, then which one of the following is correct in respect of the image seen?
- A The image will remain unchanged. ✓
- B The image will appear laterally shifted.
- C The image will appear 1·5 times brighter.
- D The image will appear 1·5 times darker.
✓ Correct answer: (A)
Science & Technology › Physics & Chemistry
CDS2025
If your image appears to be erect, no matter how far you stand from a mirror, the mirror is likely to be :
- A Plane
- B Concave
- C Convex
- D Either plane or convex ✓
✓ Correct answer: (D)
Science & Technology › Physics & Chemistry
CDS2023
A concave mirror of radius of curvature 50 cm is used to form an image of an object kept at a distance of 25 cm from the mirror on its principal axis. What will be the position of the image from the mirror ?
- A At infinity ✓
- B At 50 cm
- C At 25 cm
- D At 75 cm
✓ Correct answer: (A)
Science & Technology › Physics & Chemistry
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