Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena are responsible for this? 1. Dispersion 2. Refraction 3. Internal reflection Select the correct answer using the codes given below.

The answer is D, all three statements. A rainbow is a sequence of three optical steps inside each raindrop, and you need all three to get the bow.

• Statement 2 (refraction): Light bends as it enters the spherical drop from air into water, because water is optically denser.
• Statement 1 (dispersion): Different wavelengths bend by different amounts, so white light splits into its colours. Violet bends the most and red the least.
• Statement 3 (internal reflection): The light reflects off the back inner surface of the drop. In the primary rainbow this is a single internal reflection, and the angle is set so the colours emerge concentrated at about 42 degrees from the antisolar point.

Why the wrong options fail: A leaves out internal reflection, B leaves out dispersion, and C leaves out refraction. Each of these is a necessary step, so none of the partial combinations is complete.

Core concept: this is a classic case of refraction and dispersion combined with total internal reflection, and the same ideas explain prisms, optical fibres and atmospheric halos. For Mains, it links to Environment and Geography questions on atmospheric optics and to Science and Technology questions on the basic principles of light.

Trap: Aspirants often pick A because refraction feels like the whole story. Dispersion and internal reflection are the parts that actually produce the colour arc.