An astronomical telescope has its two lenses spaced 81.1 cm apart. If the objective lens has a focal length of 78.0 cm , what is the magnification of this telescope? Assume a relaxed eye. Follow the sign conventions.

The magnification is  

Explanation:

From the question we are told that

        The distance between the lenses is  

         The focal length of the objective lens

Generally the  length of the telescope that satisfies the condition for a relaxed eye can be mathematically represented as

Where is focal length of the eyepiece

      Making the subject the of the formula above

Now substituting value

Generally magnification can be mathematically represented as

This negative sign is a reminder that all real image are always inverted

at right angles to each other

you get 2.3=1.21*\frac{a}2 or 4.6=1.21a or a=3.802 (b)

explanation: