Science (086) — AI-generated practice question

(a) Dispersion of White Light:
The splitting of white light into its seven constituent colours on passing through a prism is called dispersion. The colours formed are Violet, Indigo, Blue, Green, Yellow, Orange, Red (VIBGYOR). Different colours bend by different angles — violet bends the most, red the least — so they separate and form a spectrum.

Diagram: [Labelled diagram showing white light entering prism face, splitting into VIBGYOR band on screen, with violet closest to base and red farthest]

(b) Newton's Experiment:
Newton placed a second identical prism in an inverted position with respect to the first. All seven colours of the spectrum passed through the second prism and recombined to give a beam of white light on the other side. This proved that sunlight is composed of seven colours.

(c) Rainbow Formation:
A rainbow forms after a rain shower when sunlight falls on tiny water droplets in the atmosphere. Each droplet acts like a small prism. Light is refracted as it enters the droplet, undergoes total internal reflection inside, and is refracted again as it exits. This causes dispersion into seven colours. The rainbow always appears in the direction opposite to the Sun.

Diagram: [Labelled diagram of a single water droplet showing — incident sunlight → refraction at entry → internal reflection → refraction at exit → dispersed colours emerging]

Source: Chapter 10, Section 10.4

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• (a): Examiners expect the definition of dispersion, mention of VIBGYOR, and the reason (different bending for different colours). A labelled diagram of Fig. 10.5 is compulsory.
• (b): The key fact is the inverted second prism recombining colours into white light — this is Newton's proof. Keep it brief.
• (c): Three key steps — refraction (entry), internal reflection, refraction (exit) — must all be named. Mention that the rainbow is always opposite to the Sun. The diagram of a single droplet (Fig. 10.8 in textbook) is expected. Do not omit "internal reflection" — it is a common exam error.