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

 

For an astronomical telescope Angular Magnification is given by

 

Solving for the focal length of the objective

 

 

Minus sign for the image angle because we know we have an inverted and virtual image.

 

 

 

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This page last updated on July 7, 2018