The correct answer is (a), (b) and (c) only. Rainbow is a meteorological phenomenon. The phenomena occur due to reflection, refraction and dispersion of light. Key Points Concept: Dispersion: The splitting of light into its component colours is called dispersion. Total Internal Reflection: Reflection of Light is the process of sending back the light rays which fall on the surface of an object. If the angle of incidence is denser medium is greater than the critical angle (the angle of incidence in the denser medium for which the angle of reflection become 90 degrees in rarer medium), then the ray is reflected back into the same medium, this phenomenon is called total internal reflection. Refraction: bending of the light beam as it travels from one medium to another is known as the refraction of light. It takes place at the boundary between the two mediums. Explanation: The rainbow formation is due to the Dispersion & Refraction of light. The different processes involved in rainbow formation are shown- [ alt="SSC JE Civil 64 10Q 3" src="https://storage.googleapis.com/tb-img/production/18/11/SSC%20JE%20Civil_64_10Q_3.PNG"> The ray is first refracted at the air-droplet interface and dispersed into 7 colors. The dispersed rays are then totally internally reflected by the droplet-air interface. The dispersed rays then undergo refraction at the droplet-air interface and finally rainbow is formed. In this, we can see that that refraction and total internal reflection plays an important role in rainbow formation but as we know splitting of white light into seven colors is caused because of phenomena known as dispersion Hence the spread in color in a rainbow on the sky is primarily due to Dispersion of sunlight