Answer:
The diagram shows a triangular prism dispersing a beam of white light into its component colors, creating a spectrum. The white light enters the prism, slows down, and bends at the first boundary due to refraction. Since different colors of light bend by different amounts, with violet bending the most and red the least, the light beam fans out into a spectrum. This spread of colors is due to the variation in the angle of refraction for different wavelengths of light. The exiting light forms a spectrum of colors from red to violet, which are labeled accordingly.