A rainbow is a natural spectrum appearing in the sky after a rain shower. It is produced by the dispersion of sunlight by tiny water droplets present in the atmosphere. When a ray of light falls on a water drop, it undergoes refraction and dispersion to form a spectrum. On reaching the opposite side of the drop, this spectrum undergoes total internal reflection (inside the drop). Arriving at the first surface of the drop, each colour is refracted back to air. The angle between the incoming and outgoing rays can be anything between 0° and about 42°. We observe a bright rainbow when the angle between the incoming and outgoing rays is close to the maximum value of 420. A rainbow is always formed in the direction opposite to that of the Sun