The Objective and the Eyepiece of a Refracting Astronomical Telescope

Multiple Choice

The objective and the eyepiece of a refracting astronomical telescope have focal lengths of 320 cm and 4.0 cm, respectively. The telescope is used to view Neptune and the final image is set at infinity. The diameter of Neptune is 4.96 × 10⁷ m and the distance from the earth at the time of observation is 4.4 × 10¹² m. What is the angle (in mrad) subtended by the final telescopic image of Neptune?

A) 0.90 mrad
B) 1.1 mrad
C) 1.3 mrad
D) 1.5 mrad
E) 1.7 mrad