Rainbow is formed when sunlight undergoes

1. Analyze the Question

The question asks for the specific optical phenomenon responsible for the formation of a rainbow when sunlight interacts with water droplets in the atmosphere.

2. Explain the Concept

A rainbow is a meteorological phenomenon caused by the interaction of sunlight with raindrops. This process involves three main stages:

• Refraction: As sunlight enters a raindrop, it slows down and bends.
• Dispersion: Because white light is composed of different colors (wavelengths), each color bends at a slightly different angle. This separates the white light into its constituent colors (the visible spectrum: Red, Orange, Yellow, Green, Blue, Indigo, Violet).
• Internal Reflection: The light hits the back of the raindrop and reflects off it, then exits the drop, undergoing further refraction.

While reflection and refraction are involved, the primary phenomenon that causes the separation of white light into the distinct colors of the rainbow is dispersion.

3. Show the Solution

• Step 1: Sunlight (white light) enters a spherical water droplet.
• Step 2: The light undergoes refraction at the surface of the droplet.
• Step 3: The light is split into its component colors because different wavelengths travel at different speeds in the water. This splitting of white light into its spectrum is the definition of dispersion.
• Step 4: The light reflects off the back of the droplet and exits, reaching our eyes as a spectrum of colors.

Among the options provided, dispersion is the most accurate description of the phenomenon that creates the color spectrum we see as a rainbow.

4. Identify the Answer

The correct option is C.

5. Exam Tip

Remember the acronym ROYGBIV for the colors of the rainbow. When you see "rainbow" and "colors" in a physics question, your mind should immediately go to dispersion. If the question asks for the cause of the color separation, it is dispersion; if it asks for the bending of light, it is refraction.