Dispersion of light — practice question

The diagram illustrates white light entering a prism. What occurs at point X, and what colour is the light that reaches the screen at point Z?

• Aat point X: dispersion only; at point Z: blue light
• Bat point X: dispersion and refraction; at point Z: blue light
• Cat point X: dispersion and refraction; at point Z: red light
• Dat point X: refraction only; at point Z: red light