f0 = 15m, fe = 1.0 cm = 10–2m.
(a) Angular magnification = f0/fe = 15/10-2 = 15 x 102 = 1500
(b) Angle subtended by the diameter of the moon = Arc/radius = (3.48 x 106)/(3.8 x 108)
Angle subtended by image
= Arc (diameter of image)/radius (focal length of objective) = d/f0 = d/15
∴ d/15 = (3.48 x 106)/(3.8 x 108)
⇒ d = (3.48 x 15)/(3.8 x 102) = 13.73 x 10-2m = 13.73 cm.