The Formation of a Rainbow

Rainbows are a beautiful natural phenomenon that occur after or during rainfall. They are formed when sunlight interacts with water droplets suspended in the air. The most accurate explanation for the formation of a rainbow is option (b) - total internal reflection and dispersion of sunlight by the water droplets suspended in the air.

Total Internal Reflection and Dispersion of Sunlight

When sunlight passes through the water droplets in the air, it undergoes refraction, which causes the light to change direction as it enters the droplet. This bending of light is due to the change in speed as it moves from one medium (air) to another (water).

Inside the droplet, the light undergoes total internal reflection. This means that the light rays are completely reflected back into the droplet instead of passing through it. The angle at which the light rays strike the inner surface of the droplet is greater than the critical angle, resulting in total internal reflection.

Dispersion of Sunlight

As the light rays undergo total internal reflection, they also undergo dispersion. Dispersion is the phenomenon where different wavelengths of light are separated or spread out. This is because different wavelengths of light bend at slightly different angles as they pass through the droplet.

The different wavelengths of light are separated within the droplet and then exit the droplet at different angles. This dispersion causes the white light to split into its component colors - red, orange, yellow, green, blue, indigo, and violet. These colors are spread out in a circular pattern.

Formation of the Rainbow

When the dispersed light exits the droplet, it undergoes further refraction as it enters the air again. This causes the light to change direction once more. The different colors of light are bent at slightly different angles as they exit the droplet, resulting in the formation of a circular arc of colors in the sky.

The observer sees this circular arc of colors as a rainbow. The colors appear in a specific order, with red on the outer edge of the arc and violet on the inner edge. This is due to the different angles at which the colors are bent and how they reach the observer's eye.

Conclusion

In conclusion, the formation of a rainbow is a result of total internal reflection and dispersion of sunlight by water droplets suspended in the air. This natural phenomenon creates a stunning display of colors in the sky, bringing joy and awe to those who witness it.

Due to T.I.R of sunlight by rain drops suspended in air. Sunlight refract two time in arain drop and reflect only one time