Because Canvas is so bad at copying images/graphs/etc over, here is another image used in one of my quizzes:

This is an image showing the refractive index as a function of wavelength for several materials, considering visible wavelengths of light.


This image is taken from Douglas Giancoli's Physics for Scientists and Engineers, 4th Ed., Pearson Publishing (2014). I have modified it somewhat by removing some curves from it, and I am using it for educational purposes only.