Dispersion is the phenomenon where white light splits into its constituent colors (spectrum) when it passes through a prism or any medium with varying refractive indices for different wavelengths. This occurs because different colors (wavelengths) of light refract by different amounts; shorter wavelengths (violet) bend more than longer wavelengths (red).
A slanted object AB is placed on one side of convex lens as shown in the diagram. The image is formed on the opposite side. Angle made by the image with principal axis is: 