The Angular Magnification of a Refracting Telescope Is 40

Multiple Choice

The angular magnification of a refracting telescope is 40.When the object and final image are both at infinity,the distance between the eyepiece and the objective is 143.5 cm.The telescope is used to view a distant radio tower.The real image of the tower,formed by the objective,is 6.0 mm in height.The focal point of the eyepiece is positioned at the real image.What is the focal length of the objective lens?

A) 138 cm
B) 139 cm
C) 140 cm
D) 141 cm