[" An infinitely long rod lies along the axis of a "],[" concave mirror of focal length 'f'.The near "],[" end of the rod is at a distance "u>f" from the "],[" mirror.Its image will have a length."],[[" 1) "(uf)/(u-f)," 2) "(uf)/(u+f)," 3) "(f^(2))/(u+f)" 4) "(f^(2))/(u-f)]]