What is dispersion of light?

Which of the following statements is incorrect?

If the refractive indices of a prism for red,yellow,and violet colours are $1.61$,$1.63$,and $1.65$ respectively,then the dispersive power of the prism will be:

If the refractive indices of crown glass for red,yellow,and violet colours are $1.5140, 1.5170$,and $1.5318$ respectively,and for flint glass these are $1.6434, 1.6499$,and $1.6852$ respectively,then the dispersive powers for crown and flint glass are respectively:

$A$ parallel beam of white light falls on a convex lens. Images of blue,yellow,and red light are formed on the other side of the lens at distances of $0.20 \ m$,$0.205 \ m$,and $0.214 \ m$ respectively. The dispersive power of the material of the lens will be:

The property of light that explains the formation of coloured images due to thick lenses is