REFLECTS the light and makes the image of the object is called a mirror.The mirror having a spherically curved reflecting SURFACE is called a spherical mirror.There are two types of spherical mirror:Concave mirror: The spherical mirror having an inward reflecting surface is called a concave mirror.The images form by the concave mirror can be real as well as virtual.Convex mirror: The mirror whose reflecting surface is outward is called a convex mirror. The images formed by the convex mirror is always virtual.The mirror formula is given by:\(\frac{1}{U} + \;\frac{1}{v} = \;\frac{1}{f}\)Where u is object distance, v is image distance and f is the FOCAL LENGTH of the mirrorCALCULATION:Given that:Object distance (u) = - 10 cmRadius of curvature (R) = - 25 cmFocal length of the concave mirror (f) = R/2 = - 25/2 = - 12.5 cmUse mirror formula:\(\frac{1}{u} + \;\frac{1}{v} = \;\frac{1}{f}\)\(\frac{1}{{ - 10}} + \;\frac{1}{v} = \;\frac{1}{{ - 12.5}}\)\(\frac{1}{v} = \;\frac{1}{{10}} - \;\frac{1}{{12.5}} = \frac{{12.5 - 10}}{{125}} = \frac{{ 2.5}}{{125}} = 1/50\)Image distance (v) = 50 cmSo option 3 is correct.