A light ray incident on a plane mirror gets reflected from it. Another plane mirror is placed such that the reflected ray from the first mirror is incident on it If the reflected ray from the second mirror travels perpendicular to the indecent ray on the first mirror, determine the angle between two plane mirrors.

An object is placed at a distance of 20 cm from a convex mirror of radius of curvature convex cm. At what distance from the object should a plane mirror be placed so that the images due to the mirror and the plane mirror are on the same plane?