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Does a prism create a rainbow?
A prism separates colors already in white light; with hypothetical zero dispersion, the paths overlap while the common beam still bends.
Try it yourself
Opens Prism Lab. Change the same thing yourself.
Transcript
Does a prism create a rainbow? White light already contains all these colors. As it enters and leaves the glass, each color bends by a different amount. Violet bends more than red, so the beam opens into a spectrum. Now turn down the dispersion. The paths come together. If every color bent equally, the prism would still bend the beam, but no rainbow would spread out. Try it yourself at Explainer Tools dot com.