Science — CBSE Class 10 board question

A rainbow appears in the sky after a rain shower, always in the direction opposite to the Sun.

It is caused by dispersion of sunlight by tiny water droplets in the atmosphere. The droplets refract and disperse sunlight, internally reflect it, and refract it again on exit, producing the VIBGYOR spectrum.

Ray Diagram:

```
Sunlight → [Water Droplet]
/ Refraction (dispersion)
/ Internal Reflection
/ Refraction (exit)
↓
Observer's Eye
(Violet at bottom, Red at top)
```

(Label: incident sunlight, refraction, internal reflection, dispersed colours — Red, Orange, Yellow, Green, Blue, Indigo, Violet)

Source: Chapter 10, Section 10.4 — Dispersion of White Light by a Glass Prism

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• Examiners expect two facts: when (after rain shower) and where (opposite to the Sun) — both needed.
• The ray diagram must show a water droplet with labelled steps: refraction → internal reflection → refraction, and the emerging colour band (VIBGYOR). A neat labelled sketch earns the diagram mark.
• Avoid writing lengthy explanations; state the cause (dispersion by water droplets) briefly.