Mars subtends an angle of 8.0 10-5 rad at the unaided eye. An astronomical telescope has

Question:

Mars subtends an angle of 8.0 × 10-5 rad at the unaided eye. An astronomical telescope has an eyepiece with a focal length of 0.032m. When Mars is viewed using this telescope, it subtends an angle of 2.8 × 10-3 rad. Find the focal length of the telescope’s objective lens.