With the help of a ray diagram, explain any phenomenon of formation of spectrum in nature.
Generated by claude-sonnet-4-6 · 2026-06-15 06:51 · grounding rag
Model Answer
Rainbow is a natural spectrum formed in the sky after rain. Tiny water droplets in the atmosphere act as small prisms. Sunlight entering a droplet gets refracted, internally reflected, and refracted again on exit, causing dispersion into VIBGYOR (Violet to Red). Red bends least and appears at the top; Violet bends most and appears at the bottom.
Ray Diagram:
```
Sunlight → [Water Droplet]
Refraction → Internal Reflection → Refraction
→ Violet (bends most)
→ ...
→ Red (bends least)
```
(Diagram shows sunlight entering droplet, undergoing internal reflection, and emerging as a colour band.)
Source: Chapter 10, Section 10.4
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Explanation
- The question asks for any natural spectrum phenomenon — Rainbow is the best choice as it is directly explained in the textbook.
- Examiners expect: name of phenomenon + cause (water droplets acting as prisms) + sequence of events (refraction → internal reflection → refraction) + mention of VIBGYOR.
- Draw a neat labelled diagram showing a raindrop with an incoming white ray, internal reflection, and emerging coloured rays. Even a rough sketch earns the diagram mark.
- Key point: Rainbow is always seen opposite to the Sun.