question_answer

An astronomical telescope uses lenses of power 10 D and 1 D. What is its magnifying power in normal adjustment?                 

Answer:

                Lens of \[\text{1 D}\] should be used as objective and lens of \[\text{1}0\text{ D}\] should be used as eyepiece. \[m=\frac{{{f}_{0}}}{{{f}_{e}}}=\frac{{{P}_{e}}}{{{P}_{f}}}=\frac{10}{1}=\mathbf{10}\].