A rainbow is formed when white light $($has all colors$)$ refracts into, reflects off the back of$,$ and refracts out of a rain drop $($many raindrops, in fact$).$

a$.)$ If all colors refracted in exactly the same way, would we be able to see a rainbow? Explain.

b$.)$ For the dispersion profile of water, violet is the color which gets most extremely refracted; it gets bent the most, and so comes out the closest to horizontal when exiting the raindrop.

This must mean that violet:

$$ experiences $---$Select$---$ the smallest the largest the same index of refraction of all the colors.

$$ travels the $---$Select$---$ the slowest the fastest the same speed as of all the colors when passing through the raindrop.

$$ if you're on the ground looking at the rainbow, you will have to look $---$Select$---$ more horizontally more vertically to see violet.

$$ hence violet will always appear at the $---$Select$---$ top bottom of a rainbow.