White light entering a glass prism emerges as a spectrum of colours. Using your knowledge of how different colours of light behave when passing through a medium, predict which colour of light would be most scattered by fine atmospheric particles, and explain how this determines the colour of the sky we see during the day.
Generated by claude-sonnet-4-6 · 2026-06-26 01:09 · grounding rag
Model Answer
From dispersion, we know that violet and blue light (shorter wavelengths) bend the most through a prism, while red light bends the least. This indicates that shorter wavelengths interact more strongly with matter.
When sunlight enters the atmosphere, fine particles (smaller than the wavelength of visible light) scatter blue light most strongly, as it has a shorter wavelength. Red light, having the longest wavelength, is scattered the least.
The scattered blue light reaches our eyes from all directions across the sky, making the sky appear blue during the day.
Source: Chapter 10, Section 10.6.2 – Why is the colour of the clear Sky Blue?
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Explanation
- The examiner expects you to link dispersion (violet/blue bends most → shorter wavelength) to scattering behaviour — this earns the first mark.
- Explicitly stating blue is most scattered due to shorter wavelength = second mark.
- Explaining that this scattered blue light enters our eyes, making the sky look blue = third mark.
- Avoid mentioning Rayleigh scattering by name — it is not in the CBSE Class 10 syllabus. Stick to "shorter wavelengths are scattered more."
- The danger-signal point (red least scattered) is a useful supporting fact but not required here.