In the given figure, `O` is a point object kept on the principal axis of a concave mirror `M` of radius of curvature `20 cm`. `P` is a prism of angle `alpha=1.8^(@)`. Light falling on the prism (at small angle of incidence) get refracted through the prism and then fall on the mirror. Rrfractive index of prism is `3//2`. Find the distance between the images formed by the concave mirror due to this light.