Rainbow is observed when the sun is

Explanation

Rainbow is observed when the Sun is low in the sky opposite to the observer facing the rain shower. The ray passing above the observer when strikes the water drops present in the air, it gets first refracted on the front surface of the drop such that the violet light deviates more than the red ray as shown in the figure. The rays further reflect back from the back surface of the drop and undergo further refraction at the front surface of the drop again. This time the violet light refracts out of the water drop such that it makes an angle of `40^(@)` with the incident ray. However, the red light makes an angular angle of `42^(@)` with the incident ray.
While observing a drop at height, the intensity of red light is more visible than violet as red light is deviated more than violet. But for a drop below or at the level of eye of the observer, the drop seems violet as the violet light is deviated less and is directed towards the observer. However, the red light is deviated away from the observer. Thus the top of the rainbow appears to be red and bottom of the rainbow appears to be violet.