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Topic Dispersion of light
Asked 6 times across 5 UPSC exams over 12 years (2013–2025), peaking in 2013.
Key insights
- Most tested in NDA — 2 of 6 PYQs
- Most asked in 2013
- Recurs across 6 years (2013–2025)
How it travelled across exams
First appearance in each exam — the same idea, reframed.
CSE 2013 → CDS 2017 → CAPF 2019 → NDA 2021 → GEO 2025
How the concept evolved
Rising — more than half its appearances (5 of 6) 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.
GEO2025
When white light propagating in air passes through a glass prism, it splits into a band of colours referred to as the white light spectrum. This phenomenon is called the dispersion of light. Among the following colours, the angle of deviation will be the highest in
- A yellow
- B green ✓
- C orange
- D red
✓ Correct answer: (B)
Science & Technology › Physics & Chemistry
NDA2023
In the dispersion of white light by a common glass prism, which one among the following is correct?
- A Red light deviates the most because red light has highest speed in prism
- B Blue light deviates the most because blue light has highest speed in prism
- C Red light deviates the most because red light has lowest speed in prism
- D Blue light deviates the most because blue light has lowest speed in prism ✓
✓ Correct answer: (D)
Science & Technology › Physics & Chemistry
NDA2021
When a light beam falls on a triangular glass prism, a band of colours is obtained. Which one of the following statements is correct in this regard ?
- A Red light bends the most, as the refractive index of glass for red light is greatest.
- B Red light bends the most, as the refractive index of glass for red light is lowest.
- C Violet light bends the most, as the refractive index of glass for violet light is greatest. ✓
- D Violet light bends the most, as the refractive index of glass for violet light is lowest.
✓ Correct answer: (C)
Science & Technology › Physics & Chemistry
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