Given :
We can see a rainbow but not a glorious rainbow in the west just as Sun was setting.
When a rainbow appears above a body of water, two complementary mirror bows may be seen below and above the horizon, originating from different light paths. Their names are slightly different. A
reflected rainbow will appear as a mirror image in the water surface below the horizon, if the surface is quiet (see photo above). The sunlight is first deflected by the raindrops, and then reflected off the body of water, before reaching the observer. The reflected rainbow is frequently visible, at least partially, even in small puddles.Where sunlight reflects off a body of water before reaching the raindrops (see diagram)
Reflection rainbow and normal rainbow, at sunset
, it may produce a reflection rainbow (see photo at the right), if the water body is large, and quiet over its entire surface, and close to the rain curtain. The reflection rainbow appears above the horizon. It intersects the normal rainbow at the horizon, and its arc reaches higher in the sky. Due to the combination of requirements, a reflection rainbow is rarely visible.
Six (or even eight) bows may be distinguished if the reflection of the reflection bow, and the secondary bow with its reflections happen to appear as well.
I hope it helps you