Shiny lawn spheres placed on pedestals are convex mirrors. One such sphere has a diameter of 40 cm. A 12 cm long robin sits in a tree 1.5 m from the sphere. (a) Where is the image of the robin? (b) How long is the image? f=R/2 to find radius 1/v=1/f-1/u to find image distance (the mirror equation) M=v/u magnification and length (maginification equation) my answer just not to sure if its right. a) f=r/2 =20/2 f=10cm u=150cm 1/v=-1/1-1/50 v= -9.4cm b) m=v/u = -9.4/150 = 0.06cm not to sure if that was the way to go.