Science — CBSE Class 10 board question

A rainbow is a natural spectrum of colours appearing in the sky, caused by dispersion of sunlight by tiny water droplets present in the atmosphere.

After rainfall, tiny water droplets remain suspended in the atmosphere. These droplets act like small prisms — they refract, internally reflect, and refract the sunlight again, dispersing it into its seven colours (VIBGYOR). Hence, a rainbow is seen only after rainfall.

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

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• The question has two parts: define rainbow + explain why only after rainfall. Address both.
• Key terms examiners look for: dispersion, water droplets act as prisms, refraction + internal reflection + refraction.
• Mentioning VIBGYOR or "seven colours" adds value but is not compulsory for 2 marks.
• Keep it concise — 2 marks = ~2 key points, no elaborate diagrams needed unless asked.