Question

why can't our eyes see a single rainbow

Answer 1

Ultraviolet light (shorter than violet) and infrared (longer than red) are both also refracted to some degree, we just can't see them because our eyes don't pick them up. Some snakes can see infrared light, though, so the rainbow would have an extra band past the red edge to them

Answer 2

ultraviolet rays ( shorter than violet) and infrared ( longer than red ) are both also refracted to some degrees we can't see them because our eyes can't pick them.

hope it may help you.........