It is a perfect inversely proportional relationship . As the distance increases, the image appears to be decrease in size . If you double the distance it will appear to be half in size . This is for straight projection . Anything other than the flat mirror will alter this and depend on the depth and extent of concave shape . the less the depth , the less the distortion .
                                 FOR EXAMPLE , if the radius of curvature is 150 cm then the focal length is 75 cm . light will converge at the focal point which is a distance of 75 cm from the mirror surface .
                                     Ray diagrams can be used to determine the position of the object , position of the image , nature of the image and size of the image ........