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Topic Total internal reflection
Asked 8 times across 4 UPSC exams over 37 years (1989–2026), peaking in 2013.
Key insights
- Most tested in CSE — 3 of 8 PYQs
- Most asked in 2013
- Recurs across 8 years (1989–2026)
How it travelled across exams
First appearance in each exam — the same idea, reframed.
CSE 1989 → CAPF 2018 → NDA 2021 → GEO 2022
How the concept evolved
Rising — more than half its appearances (5 of 8) 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 glass slab of refractive index 1·5 is cut in the shape of a parallelepiped ABCD as shown in the figure. Surface BC is polished to form a perfect reflector. Light is incident at surface AB from inside at an angle π/3. Which one of the following is the correct angle ABC (θ) such that the reflected light retraces its path?
- A π/6
- B π/3 ✓
- C π/4
- D 5π/12
✓ Correct answer: (B)
Science & Technology › Physics & Chemistry
GEO2022
The appearance of a rainbow in the sky after a rain shower is due to
- A diffraction and refraction of light in water droplets
- B total internal reflection of light in water droplets only
- C refraction of light in water droplets only
- D both total internal reflection and refraction of light in water droplets ✓
✓ Correct answer: (D)
Science & Technology › Physics & Chemistry
NDA2021
Mirage is an illustration of
- A only dispersion of light.
- B only reflection of light.
- C only total internal reflection of light.
- D both refraction and total internal reflection of light. ✓
✓ Correct answer: (D)
Science & Technology › Physics & Chemistry
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